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Calculate the average rate of change of the polynomial f(x) = x^3 - 9x over which interval?

a) (-1, 0)
b) (0, 3)
c) (3, -1)
d) (-3, 3)

1 Answer

4 votes

Final answer:

The average rate of change of the polynomial f(x) = x^3 - 9x over the interval (-3, 3) is calculated using the values of the polynomial at the endpoints of the interval and is found to be 0.

Step-by-step explanation:

To calculate the average rate of change of the polynomial f(x) = x^3 - 9x over a given interval, we apply the formula:

\[\text{Average Rate of Change} = \frac{f(b) - f(a)}{b - a}\]

Let's calculate the average rate of change for each of the provided intervals:

  1. Interval a) (-1, 0):

\[f(-1) = (-1)^3 - 9(-1) = -1 + 9 = 8\]

\[f(0) = (0)^3 - 9(0) = 0\]

\[\text{Average Rate of Change} = \frac{0 - 8}{0 - (-1)} = \frac{-8}{1} = -8\]

  1. Interval b) (0, 3):

\[f(3) = (3)^3 - 9(3) = 27 - 27 = 0\]\

[\text{Average Rate of Change} = \frac{0 - 0}{3 - 0} = 0\]

  1. Interval c) (3, -1):

\[f(3) was already calculated as 0, and f(-1) as 8\]

\[\text{Average Rate of Change} = \frac{8 - 0}{-1 - 3} = \frac{8}{-4} = -2\]

  1. Interval d) (-3, 3):

\[f(-3) = (-3)^3 - 9(-3) = -27 + 27 = 0\]

\[\text{Average Rate of Change} = \frac{0 - 0}{3 - (-3)} = \frac{0}{6} = 0\]

So the average rate of change of the polynomial on the interval (-3, 3) is 0.

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