Posted by **Jake** on Saturday, February 18, 2012 at 1:33pm.

Verify these answers~

1. For what value(s) of x does f(x)=(x^2-16)^5 have a horizontal tangent?

a) x=-4,4

b) x=-4,0,4

c) x=0

d) x=0,4

Answer is B, x=-4,0,4

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2. What is the derivative of f(x)=(3x^2+7)^3?

a) f'(x)=3(3x^2+7)^2

b) f'(x)=18(3x^2+7)^2

c) f'(x)=18x(3x^2+7)^2

d) f'(x)=3(3x^2+7)^2

Answer: C

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3. What is the y-intercept of the line that is tangent to f(x)=4/(3x+1) at (-1,-2)?

a) -5

b) -3/4

c) 3/4

d) -2

Answer: B

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4. For which point(s) on the graph of f(x)=5x/(x+2) is the slope of the tangent 2/5?

a) (-3,15)

b) (7, 35/9)

c) (3,3) and (-7,,7)

d) (24, 60/13)

Answer is C

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- Calculus-derivatives -
**Damon**, Saturday, February 18, 2012 at 5:07pm
I am only going to do one of them. That should give you the idea.

1. For what value(s) of x does f(x)=(x^2-16)^5 have a horizontal tangent?

---------------------------------

when is dy/dx = 0?

dy/dx = 5 (x^2-16)(2x)

when is that zero

When x = 0 obviously but also when

x^2 = 16

that is when x = 4 or x = -4

so

-4 , 0 , +4

a) x=-4,4

b) x=-4,0,4

c) x=0

d) x=0,4

Answer is B, x=-4,0,4

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