Question

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Find the average rate of change of f(x) = 5x2 - 4 on the interval [4, a).
Your answer will be an expression involving a.

Answer 1

5(a +4) = 5a +20

Explanation:

The average rate of change (m) on interval [p, q] is computed as ...

m = (f(q) -f(p))/(q -p)

For the given interval and function, this is ...

m = ((5a^2 -4) -(5·4^2 -4))/(a -4) = 5(a^2 -4^2)/(a -4) = 5(a +4)

The average rate of change on the interval is 5(a+4).