Answer
$$ f'(x)= -4e^{-4x+9}.$$
Work Step by Step
Recall that $(e^x)'=e^x$
Since we have
$$ f(x)=e^{-4x+9}$$
then the derivative $ f'(x)$, using the chain rule, is given by
$$ f'(x)=e^{-4x+9}(-4x+9)'=-4e^{-4x+9}.$$
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