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course Mth 158

assignment #023023. `query 23

College Algebra

05-12-2009

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21:12:50

query 3.3.16 (was 3.2.6). Key pts and behavior: far left incr, far right incr, zeros at -10, 5, 0, 5, peaks at (-8,-4), (-2, 6), (2, 10). Local min, max among listed points.List the intervals on which the function is decreasing.

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x< -8 ; -2

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21:12:57

** The function decreases until reaching the local min at (-8, -4), then increases until reaching the local max at (-2, 6).

The function then decreases to its local min at (5, 0), after which it continues increasing.

So the graph is decreasing on (-infinity, -8), on (-2, 0) and on (2, 5). **

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21:15:54

query 3.3.22 (was 3.2.12). Piecewise linear (-3,3) to (-1,0) to (0,2) to (1,0) to (3,3).Give the intercepts of the function.Give the domain and range of the function.Give the intervals on which the function is increasing, decreasing, and constant.Tell whether the function is even, odd or neither.

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Intercepts:

x-int = -1, 1

y-int = 2

Domain { -3 <- x <- 3 }

Range { 0 <- y <- 3 }

Increasing (-1,0) & (1,3)

Decreasing (-3,-1) & (0,1)

Even function

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21:16:49

** The function intersects the x axis at (-1, 0) and (1, 0), and the y axis at (0, 2).

The function decreases from (-3,3) to (-1,0) so it is decreasing on the interval (-3, -1).

The function decreases from (0, 2) to (1, 0) so it is decreasing on the interval (0, 1).

The function increases from (-1,0) to (0, 2) so it is increasing on the interval (-1, 0).

The function ioncreases from (1,0) to (3, 3) so it is increasing on the interval (1, 3).

The domain of the function is the set of possible x values, so the domain is -3 <= x <= 3, written as the interval [-3, 3].

The range of the function is the set of possible y values, so the range is 0 <= y <= 3, written as the interval [0, 3].

The function is symmetric about the y axis, with f(-x) = f(x) for every x (e.g., f(-3) = f(3) = 3; f(-1) = f(1) = 0; etc.). So the function is even. **

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21:43:28

query 3.3.28 (was 3.2.18). Piecewise linear (-3,-2) to (-2, 1) to (0, 1) to (2, 2) to (3, 0)Give the intercepts of the function.Give the domain and range of the function.Give the intervals on which the function is increasing, decreasing, and constant.Tell whether the function is even, odd or neither.

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Intercepts:

x-int = -2.3, 3

y-int = 1

Domain { -3 <= x <= 3 }

Range { -2 <= y <= 2 }

Increasing (-3,-2) & (0,2)

Decreasing (2,3)

Constant (-2,0)

This is neither odd nor even

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21:44:02

** The function intersects the x axis at (-2.25, 0) and (3, 0), and the y axis at (0, 1).

The function decreases from (2,2) to (3,0) so it is decreasing on the interval (2,3).

The function increases from (-3,-2) to (-2, 1) so it is increasing on the interval (-3, -2).

The function ioncreases from (0, 1) to (2, 2) so it is increasing on the interval (0, 2).

The function value does not change between (-2, 1) and (0, 1) so the function is constant on (-2, 0).

The domain of the function is the set of possible x values, so the domain is -3 <= x <= 3, written as the interval [-3, 3].

The range of the function is the set of possible y values, so the range is -2 <= y <= 2, written as the interval [-2, 2].

The function is not symmetric about the y axis, with f(-x) not equal to f(x) for many values of x; e.g., f(-3) is -2 and f(3) is 0. So the function is not even.

x = 3 shows us that the function is not odd either, since for an odd function f(-x) = -f(x) and for x = 3 this is not the case. **

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21:46:10

query 3.3.32 (was 3.2.24). sine-type fn (-pi,-1) to (0, 2) to (pi, -1).At what numbers does the function have a local max and what are these local maxima?At what numbers does the function have a local min and what are these local minima?

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local maxima:

f(0) = pi

local minima:

f(-pi) = -1

f(pi) = -1

Local maximum point = (0, pi)

local minimum points = (-pi, -1) & (pi, -1)

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21:46:20

** Local maximum is (0,1)

Local minimum are (-pi,-1) and (pi,-1) **

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21:54:08

query 3.3.76 / 46 (was 3.2.36) (f(x) - f(1) ) / (x - 1) for f(x) = x - 2 x^2What is your expression for (f(x) - f(1) ) / (x - 1) and how did you get this expression?How did you use your result to get the ave rate of change from x = 1 to x = 2, and what is your value?What is the equation of the secant line from the x = 1 point to the x = 2 point?

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The function I worked for #76 was f(x) = 2x^2 + x

a)

[f(x+h) - f(x)] / h

[2(x+h)^2 + (2x^2 + x) - (2x^2 + x)] / h

(2x^2 + 4xh + 2h^2) / h OR [2(x+h)^2]/h

b) x=1

h=0.5

[2(1+0.5)^2]/0.5

9

h=0.1

[2(1+0.1)^2]/0.1

24.2

h=0.01

[2(1+0.01)^2]/0.01

204.02

c)

f(1) = 2(1)^2 + 1 = 3

y -y1 = m(x-x1)

y-3 = 204.02(x-1)

y-3 = 204.02x - 204.02

y = 204.02x = 201.02

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22:38:13

** f(x) = f(1) = (x-2x^2) - (-1) = -2 x^2 + x + 1.

This factors into (2x + 1) ( -x + 1).

Since -x + 1 = - ( x - 1) we obtain

(f(x) - f(1) ) / ( x - 1) = (2x + 1) ( -x + 1) / (x - 1) = (2x + 1) * -1 = - (2x + 1).

A secant line runs from one point of the graph to another. The secant line here runs from the graph point (1, f(1) ) to the graph ponit ( x , f(x) ), and the expression we have just obtained is the slope of the secant line.

For x = 2 the expression -(2x + 1) gives us ( f(2) - f(1) ) / ( 2 - 1), which is the slope of the line from (1, f(1) ) to (2, f(2)) .

-(2 * 2 + 1) = -5, which is the desired slope.

The secant line contains the point (1, -1) and has slope 5. So the equation of the secant line is

(y - (-1) ) = -5 * (x - 1), which we solve to obtain

y = -5 x + 4. **

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22:40:31

query 3.3.36 / 50 (was 3.2.40). h(x) = 3 x^3 + 5. Is the function even, odd or neither? How did you determine algebraically that this is the case?

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h(x) = 3x^3 + 5

h(-x) = -3x^3 + 5 so not even

-h(x) = -3x^3 - 5 no not odd

The function is neither because

f(x) does not equal f(-x) nor -f(x)

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22:40:39

** h(x) = 3x^3 +5

h(-x) = 3-x^3 +5

= -3x^3 + 5

h(x) is not equal to h(-x), which means that the function is not even.

h(x) is not equal to -h(-x), since 3 x^3 + 5 is not equal to - ( -3x^3 + 5) = 3 x^3 - 5. So the function is not odd either. **

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&#Good responses. Let me know if you have questions. &#