course Mth 163

k^~assignment #005

005.

Precalculus I

02-03-2009

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17:07:47

`q001. Note that this assignment has 8 questions

Evaluate the function y = x^2 for x values -3, -2, -1, 0, 1, 2, and 3. What are your y values?

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RESPONSE -->

y=9,4,1,0,1,4,9

confidence assessment: 3

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17:07:58

You should have obtained y values 9, 4, 1, 0, 1, 4, 9, in that order.

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RESPONSE -->

this is what i got

self critique assessment: 3

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17:09:26

`q002. Evaluate the function y = 2^x for x values -3, -2, -1, 0, 1, 2, and 3. What are your y values?

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RESPONSE -->

y=.125, .25, - 2, 1, 2, 8

confidence assessment: 3

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17:09:51

By velocity exponents, b^-x = 1 / b^x. So for example 2^-2 = 1 / 2^2 = 1/4. Your y values will be 1/8, 1/4, 1/2, 1, 2, 4 and 8. Note that we have used the fact that for any b, b^0 = 1. It is a common error to say that 2^0 is 0. Note that this error would interfere with the pattern or progression of the y values.

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RESPONSE -->

ok

self critique assessment: 3

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17:11:41

`q003. Evaluate the function y = x^-2 for x values -3, -2, -1, 0, 1, 2, and 3. What are your y values?

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RESPONSE -->

y= .111, .25, 1, not possible, 1, .25, .111

confidence assessment: 3

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17:11:50

By the laws of exponents, x^-p = 1 / x^p. So x^-2 = 1 / x^2, and your x values should be 1/9, 1/4, and 1. Since 1 / 0^2 = 1 / 0 and division by zero is not defined, the x = 0 value is undefined. The last three values will be 1, 1/4, and 1/9.

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RESPONSE -->

ok

self critique assessment: 3

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17:12:55

`q004. Evaluate the function y = x^3 for x values -3, -2, -1, 0, 1, 2, and 3. What are your y values?

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RESPONSE -->

y= -27, -8, -1, 0, 1, 8, 27

confidence assessment: 3

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17:13:47

The y values should be -27, -8, -1, 0, 1, 4, 9.

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RESPONSE -->

I got the same except 2^3 is not 4 its 8 and 3^3 is 27 not 9

self critique assessment: 3

You are correct.

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17:22:35

`q005. Sketch graphs for y = x^2, y = 2^x, y = x^-2 and y = x^3, using the values you obtained in the preceding four problems. Describe the graph of each function.

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RESPONSE -->

y=x^2 is just a parabola with the vertex at 0,0...y=2^x is a half of a porabola that stays positive and crosses throught the origion...y=x^-2 is just a straight line lying under the x axis...y=x^3 is a porabola that crosses the origion with one half sloping negatively and the other half is positive.

confidence assessment: 3

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17:23:40

The graph of y = x^2 is a parabola with its vertex at the origin. It is worth noting that the graph is symmetric with respect to the y-axis. That is, the graph to the left of the y-axis is a mirror image of the graph to the right of the y-axis.

The graph of y = 2^x begins at x = -3 with value 1/8, which is relatively close to zero. The graph therefore starts to the left, close to the x-axis. With each succeeding unit of x, with x moving to the right, the y value doubles. This causes the graph to rise more and more quickly as we move from left to right. The graph intercepts the y-axis at y = 1.

The graph of y = x^-2 rises more and more rapidly as we approach the y-axis from the left. It might not be clear from the values obtained here that this progression continues, with the y values increasing beyond bound, but this is the case. This behavior is mirrored on the other side of the y-axis, so that the graph rises as we approach the y-axis from either side. In fact the graph rises without bound as we approach the y-axis from either side. The y-axis is therefore a vertical asymptote for this graph.

The graph of y = x ^ 3 has negative y values whenever x is negative and positive y values whenever x is positive. As we approach x = 0 from the left, through negative x values, the y values increase toward zero, but the rate of increase slows so that the graph actually levels off for an instant at the point (0,0) before beginning to increase again. To the right of x = 0 the graph increases faster and faster.

Be sure to note whether your graph had all these characteristics, and whether your description included these characteristics. Note also any characteristics included in your description that were not included here.

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RESPONSE -->

I messed up on x^-2

self critique assessment:

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17:23:42

The graph of y = x^2 is a parabola with its vertex at the origin. It is worth noting that the graph is symmetric with respect to the y-axis. That is, the graph to the left of the y-axis is a mirror image of the graph to the right of the y-axis.

The graph of y = 2^x begins at x = -3 with value 1/8, which is relatively close to zero. The graph therefore starts to the left, close to the x-axis. With each succeeding unit of x, with x moving to the right, the y value doubles. This causes the graph to rise more and more quickly as we move from left to right. The graph intercepts the y-axis at y = 1.

The graph of y = x^-2 rises more and more rapidly as we approach the y-axis from the left. It might not be clear from the values obtained here that this progression continues, with the y values increasing beyond bound, but this is the case. This behavior is mirrored on the other side of the y-axis, so that the graph rises as we approach the y-axis from either side. In fact the graph rises without bound as we approach the y-axis from either side. The y-axis is therefore a vertical asymptote for this graph.

The graph of y = x ^ 3 has negative y values whenever x is negative and positive y values whenever x is positive. As we approach x = 0 from the left, through negative x values, the y values increase toward zero, but the rate of increase slows so that the graph actually levels off for an instant at the point (0,0) before beginning to increase again. To the right of x = 0 the graph increases faster and faster.

Be sure to note whether your graph had all these characteristics, and whether your description included these characteristics. Note also any characteristics included in your description that were not included here.

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RESPONSE -->

self critique assessment: 3

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17:25:31

`q006. Make a table for y = x^2 + 3, using x values -3, -2, -1, 0, 1, 2, 3. How do the y values on the table compare to the y values on the table for y = x^2? How does the graph of y = x^2 + 3 compare to the graph of y = x^2?

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RESPONSE -->

the values are the same but 3 more than the ones on the previous table and the graph looks the same it is a parabola that has a positive opening and the only difference is that it is moved up the y axis 3 places

confidence assessment: 3

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17:25:42

A list of the y values will include, in order, y = 12, 7, 4, 3, 4, 7, 12.

A list for y = x^2 would include, in order, y = 9, 4, 1, 0, 1, 4, 9.

The values for y = x^2 + 3 are each 3 units greater than those for the function y = x^2.

The graph of y = x^2 + 3 therefore lies 3 units higher at each point than the graph of y = x^2.

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RESPONSE -->

ok

self critique assessment: 3

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17:29:27

`q007. Make a table for y = (x -1)^3, using x values -3, -2, -1, 0, 1, 2, 3. How did the values on the table compare to the values on the table for y = x^3? Describe the relationship between the graph of y = (x -1)^3 and y = x^3.

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RESPONSE -->

The values are (-64, -27, -8, -1, 0, 1, 8) versus the first one which was (-27, -8, -1, 0, 1, 8, 27) and the graph looks the same however it crosses the x axis to the right one more unit or at about 1, 2 versus 0

confidence assessment: 3

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17:29:33

The values you obtained should have been -64, -27, -8, -1, 0, 1, 8.

The values for y = x^3 are -27, -8, -1, 0, 1, 8, 27.

The values of y = (x-1)^3 are shifted 1 position to the right relative to the values of y = x^3. The graph of y = (x-1)^3 is similarly shifted 1 unit to the right of the graph of y = x^3.

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RESPONSE -->

ok

self critique assessment: 3

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17:33:18

`q008. Make a table for y = 3 * 2^x, using x values -3, -2, -1, 0, 1, 2, 3. How do the values on the table compare to the values on the table for y = 2^x? Describe the relationship between the graph of y = 3 * 2^x and y = 2^x.

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RESPONSE -->

y=.375, .75, 1.5, 3, 6, 12, 24 These new values were all multiplied by 3 and the new graph is the same as the old except it is moved to the left by -3

confidence assessment: 3

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17:33:24

You should have obtained y values 3/8, 3/4, 3/2, 3, 6, 12 and 24.

Comparing these with the values 1/8, 1/4, 1/2, 1, 2, 4, 8 of the function y = 2^x we see that the values are each 3 times as great.

The graph of y = 3 * 2^x has an overall shape similar to that of y = 2^x, but each point lies 3 times as far from the x-axis. It is also worth noting that at every point the graph of y = 3 * 2^x is three times as the past that of y = 2^x.

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RESPONSE -->

self critique assessment:

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&#Your work looks good. See my notes. Let me know if you have any questions. &#

course Mth 163

mÇدNڀ켓assignment #005

005. `query 5

Precalculus I

02-03-2009

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17:41:37

query introduction to basic function families problem 1 on basic graphs

Why is the graph of y = x a straight line?

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RESPONSE -->

Because there is no variation the only solution to any possible number for example y=456, x=456 are going to equal each other

confidence assessment: 3

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17:41:56

** Since y = x the rise and run between any two points on the graph are equal, which makes the slope 1. A graph with constant slope is a straight line. **

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RESPONSE -->

I did forget about the slope being one

self critique assessment: 3

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17:44:19

why is y = x^2 symmetric about x = 0 (i.e., taking the same values on either side of x = 0)

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RESPONSE -->

because this works the same as a linear the values equal each other but because they are squared there can never be a negative number therefore there is only positive slopes and they meet at 0 which makes them symmetric

confidence assessment: 3

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17:44:30

** The graph of y = x^2 is symmetric about x = 0 because (-x)^2 = x^2. Thus for any point on the x axis the y values at that point and at the point on the opposite side of the origin are equal, so that the graph on one side of the y axis is a 'reflection' of the graph on the other side. **

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RESPONSE -->

ok

self critique assessment: 3

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17:46:30

why does y = 2^x keep increasing as x increases, and why does the graph approache the x axis for negative values of x

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RESPONSE -->

because it is like you are taking the reciprical and dividing the two to get a smaller number and as x increases your multiplying 2 to something and it increases the value

confidence assessment: 3

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17:47:19

** GOOD STUDENT RESPONSE: y = 2^x will increase as x increases on the positive side because x is the value of the exponent. This will cause the y value to double from its last value when you move one unit in the positive x direction.

On the negative side of the y axis y = 2^x will approach the x axis because a negative exponent causes the value to invert into a fractional value of itself--i.e., 2^(-x) = 1 / 2^x. As we move one unit at a time negatively the value will become one half of the previous value so it will never quite reach y = 0. **

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RESPONSE -->

ok I couldnt think of the words to quite describe this I knew what I wanted to say but didnt know how to get it out

self critique assessment: 3

I understood what you were saying. You're doing a good job.

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17:48:46

why is y = x^3 antisymmetric about x = 0 (i.e., taking the same values except for the - sign on opposite sides of x = 0)

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RESPONSE -->

beacuse unlike being squared when something is to the third it is multiplied like -3*-3*-3 which is -27 the negative value is not taken out which in turn means that there has to be a negative slope at some point

confidence assessment: 3

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17:49:02

** y = x^3 is antisymmetric because if you cube a negative number you get a negative, if you cube a positive number you get a positive, and the magnitude of the cubed number is the cube of the magnitude of the number. So for example (-3)^2 = -27 and 3^3 = 27; the points (-3, -27) and (3, 37) are antisymmetric, one being `down' while the other is `up'.

GOOD STUDENT RESPONSE: y = x^3 is antisymmetric about x = 0 because the exponent is an odd number. This will cause negative x values to have a negative y result. The absolute value of the negative y result will be equivalent to its corresponding positive y value. **

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RESPONSE -->

ok

self critique assessment: 3

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17:50:32

why do y = x^-2 and y = x^-3 rise more and more steeply as x approaches 0, and why do their graphs approach the x axis as we move away from the y axis.

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RESPONSE -->

Im actually not really sure about the process of this graph

confidence assessment: 3

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17:51:42

** And as x approaches 0 the expressions x^-2 and x^-3, which mean 1 / x^2 and 1 / x^3, have smaller and smaller denominators. As the denominators approach zero their reciprocals grow beyond all bound.

y = x^-2 and y = x^-3 rise more and more steeply as x approaches zero because they have negative exponents they become fractions of positive expressions x^2 and x^3 respectively which have less and less slope as they approach zero. As x^2 and x^3 approach zero and become fractional, x^-2 and x^-3 begin to increase more and more rapidly because thier functions are then a whole number; (1) being divided by a fraction in which the denominator is increasing at an increasing rate.

As y = x^-2 and y = x^-3 move away from the y-axis they approach the x-axis because they have negative exponents. This makes them eqivalent to a fraction of 1 / x^2 or 1 / x^3. As x^2 and x^3 increase in absolute value, the values of y = x^-2 and y = x^-3 constantly close in on the x-axis by becoming a portion of the remaining distance closer, they will never reach x = zero though as this would be division by zero (since it is a fraction) **

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RESPONSE -->

this makes more sense to me sometimes it is hard to see the process even when laying it all out

self critique assessment: 3

If you don't completely understand a given solution, it's a very good idea to use the words as a guideline and reconstruct the corresponding solution on paper.

The key here is to understand the rules for negative exponents, and what happens as x gets closer and closer to zero.

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17:52:45

query problem 2. family y = x^2 + c

Explain why the family has a series of identical parabolas, each 1 unit higher than the one below it.

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RESPONSE -->

beacuse the c variable only changes the y axis it raises or lowers the vertex depending on whether the value is positive or negative

confidence assessment: 3

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17:52:54

** GOOD STUDENT RESPONSE: The graph of y = x^2 + c, with c varying from -5 to 4 is a series of identical parabolas each 1 unit higher than the one below it. The c value in the quadratic equation has a direct impact on the vertical shift. The vertex of the graph will be shifted vertically by the amount of the c value, so every time c increases by 1 the graph is raised 1 unit. **

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RESPONSE -->

ok

self critique assessment: 3

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17:53:41

query problem 4. describe the graph of the exponential family y = A * 2^x for the values A = -3 to 3.

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RESPONSE -->

The only change that occurs is that the vertex moves along the x axis from -3 to positive 3

confidence assessment: 3

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17:53:47

** This family includes the functions y = -3 * 2^x, y = -2 * 2^x, y = -1 * 2^x, y = 0 * 2^x, y = 1 * 2^x, y = 2 * 2^2 and y = 3 * 2^x. Each function is obtained by vertically stretching the y = 2^x function.

y = -3 * 2^x, y = -2 * 2^x, y = -1 * 2^x all vertically stretch y = 2^x by a negative factor, so the graphs all lie below the x axis, asymptotic to the negative x axis and approaching negative infinity for positive x. They pass thru the y axis as the respective values y = -3, y = -2, y = -1.

y = 1 * 2^x, y = 2 * 2^x, y = 3 * 2^x all vertically stretch y = 2^x by a positive factor, so the graphs all lie above the x axis, asymptotic to the negative x axis and approaching positive infinity for positive x. They pass thru the y axis as the respective values y = 1, y = 2, y = 3.

y = 0 * 2^x is just y = 0, the x axis.

Of course the functions for fractional values are also included (e.g., y = -2.374 * 2^x) but only the integer-valued functions need to be included in order to get a picture of the behavior of the family. **

STUDENT QUESTION: Ok, it was A = -3 to 3. I understand how to substitute these values into y = A * 2^x. I knew that is was an asymptote, but I'm a little confused as to how to graph the asymptote.

INSTRUCTOR RESPONSE: For each value of A you have a different function. For A = -3, -2, -1, 0, 1, 2, 3you have seven different functions, so you will get 7 different graphs.

Each graph will contain the points for all values of x. For example the A = -3 function is y = -3 * 2^x. This function has basic points (0, -3) and (1, -6). As x takes on the negative values -1, -2, -3, etc., the y values will be -1.5, -.75, -.375, etc.. As x continues through negative values the y values will approach zero. This makes the y axis a horizontal asymptote for the function.

You should figure out the x = 0 and x = 1 values for every one of these seven functions, and you should be sure you understand why each function approaches the negative x axis as an asymptote. *&*&

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RESPONSE -->

ok

self critique assessment: 3

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17:55:23

describe the graph of the exponential family y = 2^x + c for the values c = -3 to 3.

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RESPONSE -->

The graph looks the same but changes where it crosses the y axis it always crosse just above the value that c states

confidence assessment: 3

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17:55:29

** There are 7 graphs, including y = 2^x + 0 or just y = 2^x.

The c = 1, 2, 3 functions are y = 2^x + 1, y = 2^x + 2 and y = 2^x + 3, which are shifted by 1, 2 and 3 units upward from the graph of y = 2^x.

The c = -1, -2, -3 functions are y = 2^x - 1, y = 2^x - 2 and y = 2^x - 3, which are shifted by 1, 2 and 3 units downward from the graph of y = 2^x. **

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RESPONSE -->

ok

self critique assessment: 3

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17:57:31

query problem 5. power function families

Describe the graph of the power function family y = A (x-h) ^ p + c for p = -3: A = 1, h = -3 to 3, c = 0.

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RESPONSE -->

The graph -5 and takes a steep negative slope and then a stragiht positve line back up and then a steep negative slope once again

confidence assessment: 3

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17:57:53

** GOOD STUDENT RESPONSE: I sketched the graph of the power function family y = A (x-h)^p + c for p = -3: A = 1: h = -3 to 3, c = 0. Beginning on the left side of the graph the curve was infinitely close to its asmptote of y = 0. This was determined by the value of c. As we move from left to right the curves decreased at an increasing rate, approaching thier vertical asmptotes which was determined by thier individual values of h. The curves broke at x = c as this value was never possible due to division by zero. The curves resurfaced on the graph high on the right side of thier vertical asymptotes and from there they decreased at a decreasing rate, once again approaching thier horizontal asymptote of y = 0.

INSTRUCTOR COMMENTS: Only the h value changes. p=-3, A=1 and c=0, so the functions are y = 1 * (x-h)^-3 or y = (x-h)^-3.

For h = -3 to 3 the functions are y = (x - (-3))^-3, y = (x - (-2))^-3, y = (x - (-1))^-3, y = (x - 0)^-3, y = (x - 1)^-3, y = (x - 2)^-3, y = (x - 3)^-3.

These graphs march from left to right, moving 1 unit each time. Be sure you see in terms of the tables why this happens. **

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RESPONSE -->

ok

self critique assessment: 3

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17:58:39

query problem 10 illumination. What function did you evaluate to get your results?

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RESPONSE -->

confidence assessment:

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17:58:58

** I determined the illumination y from a certain florescent bulb at the distances of 1, 2, 3, and 4 units using the generalized power function for p = -1 with A = 370, h = 0 and c = 0. This power function is

y = A (x- h)^p + c = 370 (x - 0)^(-1) + 0, or just

y = 370 x^-1. **

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RESPONSE -->

I didnt really understand this one

self critique assessment: 3

The generalized power function has form

y = A * ( x - h ) ^ p + c.

A = 370, h =0 and c = 0 are all given quantities in this problem.

Plug these quantities into the form

y = A * ( x - h ) ^ p + c

and you will get

y = 370 (x - 0)^(-1) + 0, which simplifies to

y = 370 x^(-1).

The illumination is y, the distances are x values. Plug in x = 1, then x = 2, then x = 3, then x = 4. Each x value will give you a y value.

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17:59:35

Determine the illumination at distances of 1, 2, 3 and 4 units, and sketch a graph.

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RESPONSE -->

confidence assessment:

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18:00:01

** Student Solution:

For x=1 we obtain y=370(-1-0) ^-1=370

For x=2 we obtain y=370(2-0)^-1=185

For x=3 we obtain y=370(3-0)^-1 =123.3

For x=4we obtain y=370(4-0)^-1=92.5**

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RESPONSE -->

I dont get where the 370 is coming from?

self critique assessment: 3

It was given in the statement of the problem.

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18:00:34

Query Add comments on any surprises or insights you experienced as a result of this assignment.

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RESPONSE -->

This assignement did show me how easy it is to graph any functin with just a couple simple points.

self critique assessment: 3

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18:00:55

** STUDENT COMMENT: I have never worked with graphs in the power family, and very little in the exponential family. I am always amazed at the patterns that a function produces. It helps me understand the equation so much better than a list of numbers. I do feel that I need the data table with the graph to fully understand it.

INSTRUCTOR RESPONSE: The data table is certainly helpful, especially when you see the reasons for the number patterns in the formula as well as you do. **

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RESPONSE -->

this was a useful insight as well

self critique assessment: 3

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&#Good responses. See my notes and let me know if you have questions. &#

course mth 163

׺~~ZarEL̓wassignment #006

006.

Precalculus I

02-03-2009

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18:04:26

`q001. Note that this assignment has 10 questions

Recall that the graph of y = x^2 + 3 was identical to the graph of y = x^2, except that it was raised 3 units. This function is of the form y = x^2 + c. In the case of this specific function, c = 3. What function would this form give us for c = -1? How would the graph of this function compare with the graph of y = x^2?

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RESPONSE -->

The graph x^2 is a porabola with the origion as its vertex but x^2-1 is the same graph but the vertex is moved down the y axis by a -1

confidence assessment: 3

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18:04:33

If c = -1 the form y = x^2 + c gives us y = x^2 - 1. Every value on a table of this function would be 1 less than the corresponding value on a table of y = x^2, and the graph of y = x^2 - 1 will lie 1 unit lower at each point then the graph of y = x^2.

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RESPONSE -->

ok

self critique assessment: 3

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18:05:35

`q002. Suppose that we wish to graph the functions y = x^2 + c for c = -3, then for c = -2, then for c = -1, then for c = 0, then for c = 1, then for c = 2, then for c = 3. If all these functions were plotted on the same set of coordinate axes, what would the final graph look like? It is suggested that you actually sketch your graph and describe your sketch.

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RESPONSE -->

It would look like many porabolas they would all look the same but would all have a vertex at one unit either +1 or -1 from the next

confidence assessment: 3

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18:05:44

The graph of the c= -3 function y = x^2 - 3 will lie 3 units lower than the graph of y = x^2.

The graph of the c= -2 function y = x^2 - 2 will lie 22222 units lower than the graph of y = x^2.

The progression should be obvious. The graph of the c= 3 function y = x^2 + 3 will lie 3 units higher than the graph of y = x^2.

The final graph will therefore show a series of 7 functions, with the lowest three units below the parabolic graph of y = x^2 and the highest three units above the graph of this function. Each graph will lie one unit higher than its predecessor.

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RESPONSE -->

ok

self critique assessment: 3

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18:07:26

`q003. The function y = (x -1)^3 is of the form y = (x -k)^3 with k = 1. What function would this form give us for k = 3? How would the graph of this function compare with that of y = x^3?

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RESPONSE -->

The graph of x^3 is a nonsymetrical porabola with the vertex at 0,0 and the only difference in these two is that the vertex is moved over to the right by 3 still on the x axis

confidence assessment: 3

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18:07:34

Recall how the graph of y = (x-1)^3 lies one unit to the right of the graph of y = x^3. The k = 3 function y = (x -3)^3 will lie 3 units to the right of the graph of y = x^3.

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RESPONSE -->

ok

self critique assessment: 3

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18:08:15

`q004. Suppose we wish to graph the functions y = (x -k)^3 for k values 2, then 3, then 4. If we graph all these functions on the same set of coordinate axes, what will the graph look like? It is suggested that you actually sketch your graph and describe your sketch.

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RESPONSE -->

they would each cross the x axis at the different points that k is changed to

confidence assessment: 3

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18:08:23

The k = 2 graph will lie 2 units to the right of the graph of y = x^3, and the k = 4 graph will lie 4 units to the right. The three graphs will all have the same shape as the y = x^3 graph, but will lie 2, 3 and 4 units to the right.

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RESPONSE -->

ok

self critique assessment: 3

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18:10:21

`q005. The function y = 3 * 2^x is of the form y = A * 2^x for A = 3. What function would this form give us for A = 2? How would the graph of this function compare with that of y = 2^x?

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RESPONSE -->

2^x is a positive sloping line that moves away from the x as it moves from the y and the only difference when a=2 is that the start of the graph is moved to the left by about -2

confidence assessment: 3

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18:10:27

As we saw earlier, the graph of y = 3 * 2^x lies 3 times as far from the x-axis as a graph of y = 2^x and is at every point three times as steep. We would therefore expect the A = 2 function y = 2 * 2^x to lie 2 times is far from the x-axis as the graph of y = 2^x.

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RESPONSE -->

ok

self critique assessment: 3

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18:11:10

`q006. Suppose we wish to graph the functions y = A * 2^x for values A ranging from 2 to 5. If we graph all such functions on the same set of coordinate axes, what will the final graph look like? It is suggested that you actually sketch your graph and describe your sketch.

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RESPONSE -->

They all look the same functionally but they difffer only from where they orgionate on the x axis

confidence assessment: 3

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18:11:17

These graphs will range from 2 times as far to 5 times as far from the x-axis as the graph of y = 2^x, and will be from 2 to 5 times as steep. The y intercepts of these graphs will be (0,2), (0, 3), (0, 4), (0,5).

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RESPONSE -->

ok

self critique assessment: 3

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18:12:39

`q007. What is the slope of a straight line connecting the points (3, 8) and (9, 12)?

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RESPONSE -->

4/6

confidence assessment: 3

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18:12:47

The rise between the points is from y = 8 to y = 12. This is a rise of 12-8 = 4.

The run between these points is from x = 3 to x = 9, a run of 9 - 3 = 6.

The slope between these points is therefore rise/run = 4/6 = 2/3, with decimal equivalent .6666....

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RESPONSE -->

ok

self critique assessment: 3

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18:16:17

`q008. What are the coordinates of the t = 5 and t = 9 points on the graph of y = 2 t^2 + 3? What is the slope of the straight line between these points?

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RESPONSE -->

(5, 67) (9, 1027) and the slope would be 960/4=240

confidence assessment: 3

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18:17:13

The t = 5 value is y = 2 * 5^2 + 3 = 2 * 25 + 3 = 50 + 3 = 53.

The t = 9 value is similarly calculated. We obtain y = 165.

The rise between these points is therefore 165-53 = 112. The run is from t = 5 to t = 9, a run of 9 - 5 = 4. This slope of a straight line connecting these points is therefore rise/run = 112/4 = 28.

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RESPONSE -->

I must of messed up on my algebra I see the mistakes I made now

self critique assessment: 3

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18:18:44

`q009. Suppose y = 2 t^2 + 3 represents the depth, in cm, of water in a container at clock time t, in seconds. At what average rate does the depth of water change between t = 5 seconds and t = 9 seconds?

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RESPONSE -->

109

confidence assessment: 3

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18:19:27

The t = 5 second and t = 9 second depths are easily calculated to be y = 53 cm and y = 165 cm. The depth therefore changes from 53 cm to 165 cm, a change of 165 cm - 53 cm = 112 cm, in the 4 seconds between the to clock times. The average rate of depth changes therefore 112 cm/(4 seconds) = 28 cm/second.

We note that this calculation is identical to the calculation of the slope of the straight line connecting the t = 5 and t = 9 points of the graph y = 2 t^2 + 3.

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RESPONSE -->

Oh this makes complete sense now I was just taking the average of the two y values

self critique assessment: 3

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18:20:01

`q010. If we have a graph of depth y vs. clock time t, then how to we know that the slope of a straight line connecting two points of the graph represents the average rate at which depth changes over the corresponding time interval?

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RESPONSE -->

because the slope is the change in the graph it represents how much change occurs between each point

confidence assessment: 3

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18:20:09

The rise of the graph represents the change in the depth y and the run represents the change clock time t. The slope, which is rise/run, therefore represents change in depth/change in clock time, which is the average rate at which the depth changes.

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RESPONSE -->

ok

self critique assessment: 3

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&#Your work looks very good. Let me know if you have any questions. &#