1967 AHSME Problems/Problem 6

Problem

If $f(x)=4^x$ then $f(x+1)-f(x)$ equals:

$\text{(A)}\ 4\qquad\text{(B)}\ f(x)\qquad\text{(C)}\ 2f(x)\qquad\text{(D)}\ 3f(x)\qquad\text{(E)}\ 4f(x)$

The desired expression is equal to $4^{x+1} - 4^{x}$ Using the fact that $4^{x+1}$ = $4^{x}*4$ , we see that the answer is $3*4^{x}$ $\fbox{D}$

1967 AHSME (Problems • Answer Key • Resources)
Preceded by Problem 5	Followed by Problem 7
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