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AP® Calculus AB-BC

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Rate of Change: Do You Know What it Means and How to Use it?

APCALC-YNBPCB

Let $f(x)=\cfrac{5}{x}$. If the rate of change at $x=c$ is four times its rate of change at $x=3$, then $c=\underline{\hspace{2cm}}$.

A

$\cfrac{3}{4}$

B

$\pm 2 \sqrt{3}$

C

$\pm \cfrac{9}{4}$

D

$\pm \cfrac{3}{2}$