How do you find the instantaneous rate of change of the function $f (x) = - 9 x^{2} - x$ $f(x) = -9x^(2) -x$ when x=-4?

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Answer 1 · 2016-03-21T10:34:57

71

The instantaneous rate of change is the value of the derivative at x = -4.

$f'(x) = -18x - 1$

$rArr f'(-4) = -18(-4) - 1 = 72 - 1 = 71$

How do you find the instantaneous rate of change of the function f(x) = -9x^(2) -xf(x)=−9x2−xf(x) = -9x^(2) -x when x=-4?