View source for 1967 AHSME Problems/Problem 6

== Problem ==
If <math>f(x)=4^x</math> then <math>f(x+1)-f(x)</math> equals:

<math> \text{(A)}\ 4\qquad\text{(B)}\ f(x)\qquad\text{(C)}\ 2f(x)\qquad\text{(D)}\ 3f(x)\qquad\text{(E)}\ 4f(x) </math>

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

== See also ==
{{AHSME 40p box|year=1967|num-b=5|num-a=7}}  

[[Category:Introductory Algebra Problems]]
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