How to find instantaneous rate of change for $f(x) = -x^4+1$ at (3, -80)?

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Answer 1 · 2017-03-24T04:30:44

$f'(3)=-108$

The instant rate of change of a function $f$ at $x=a$ is given by $f'(a)$ .

Here, $f(x)=-x^4+1$ . The derivative of this is $f'(x)=-4x^3$ . The instant rate of change of $f$ at $x=3$ , then, is $f'(3)=-4(3^3)=-108$ .

How to find instantaneous rate of change for f(x) = -x^4+1 f(x) = -x^4+1 at (3, -80)?