Asst 11 Comp

course Mth271

???}????????assignment #011

011. `query 11

Applied Calculus I

03-30-2009

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17:49:06

1.6.16 (was 1.6.14 intervals of cont for (x-3)/(x^2-9)

What are the intervals of continuity for the given function?

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RESPONSE -->

This function is continuos at all real numbers because it is just a polynomial equation.

confidence assessment: 1

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17:50:46

The function is undefined where x^2 - 9 = 0, since division by zero is undefined.

x^2 - 9 = 0 when x^2 = 9, i.e., when x = +-3.

So the function is continuous on the intervals (-infinity, -3), (-3, 3) and (3, infinity).

The expression (x - 3) / (x^2 - 9) can be simplified. Factoring the denominator we get

(x - 3) / [ (x - 3) ( x + 3) ] = 1 / (x + 3).

This 'removes' the discontinuity at x = +3. However in the given fom (x-3) / (x^2 + 9) there is a discontinuity at x = -3. **

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RESPONSE -->

My number 16 problem was different than this I believe. My equation was 3 - 2x - x^2

I believe this is problem 19 maybe? If so I can see that the function is undefined when x^2 - 9 = 0.

self critique assessment: 2

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17:53:41

1.6.24 (was 1.6.22 intervals of cont for |x-2|+3, x<0; x+5, x>=0

What are the intervals of continuity for the given function?

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RESPONSE -->

My number 24 Is the cont for [[x-2]] + x.

My answer was that the function is continous at all 2x + x values. I don't believe this is right. I still am having a problem with the lowest integer function. I understand we are to round to the lowest integar, but how do we do this when we have something other than just a plain integer?

confidence assessment: 0

For example, if x = 3.9 we have [ [ x - 2 ] ] = [ [3.9 - 2]] = [ [ 1.9] ] = 1.

[[ 1.9 ]] is the greatest integer less than or equal to 1.9, which is 1.

if x = 3.99 we have [ [ x - 2 ] ] = [ [3.99 - 2]] = [ [ 1.99] ] = 1

[[1.99]] is still 1.

if x = 3.99999 we have [ [ x - 2 ] ] = [ [3.99999 - 2]] = [ [ 1.99999] ] = 1

[[1.99999]] is still 1.

However as soon a x = 4 we get [[4-2]] = [[2]] = 2.

[[ 2 ]] is the greatest integer less than or equal to 2, which since 2 is an integer is just 2.

Now if x = 3.9 we have [[x-2]] + x = [[3.9 - 2]] + 3.9 = 1 + 3.9 = 4.9.

If x = 4 we get [[x-2]] + x = 6.

What happens for values of x between 3.9 and 4, especially for values of x that approach 4 as a limit?

How can you use these examples to understand this function and determine its intervals of continuity?

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17:54:07

The graph of y = |x-2|+3 is translated 2 units in the x direction and 3 in the y direction from the graph of y = |x|. It forms a V with vertex at (2, 3).

The given function follows this graph up to x = 0. It has slope -1 and y-intercept at y = | 0 - 2 | + 3 = 5.

The graph then follows y = x + 5 for all positive x. y = x + 5 has y-intercept at y = 5. From that point the graph increases along a straight line with slope 1.

So the graph of the given function also forms a V with vertex at (0, 5).

Both functions are continuous up to that point, and both continuously approach that point. So the function is everywhere continuous. **

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RESPONSE -->

See previous note.

self critique assessment: 1

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17:55:29

1.6.66 (was 1.6.54 lin model of revenue for franchise

Is your model continuous? Is actual revenue continuous?

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RESPONSE -->

Because the model is linear, it would be a continuous model, however actual revenue probably would not be continuous because it is nearly impossible to expect revenues to be smooth, with no jumps, leaps, or gaps.

confidence assessment: 2

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17:55:50

revenue comes in 'chunks'; everytime someone pays. So the actual revenue 'jumps' with every payment and isn't continuous. However for a franchise the jumps are small compared to the total revenue and occur often so that a continuous model isn't inappropriate for most purposes. **

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RESPONSE -->

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self critique assessment: 3

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17:55:54

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

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RESPONSE -->

self critique assessment: 3

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