I am in dire need of assistance!!!

JeffM

Elite Member
Joined
Sep 14, 2012
Messages
6,828
There are at least three ways to attack this problem.

The most general is to realize that

[math]4^n - 1 = (2^2)^n - 1 = 2^{2n} - 1.[/math]
Can you see the next step?
 

Harry_the_cat

Elite Member
Joined
Mar 16, 2016
Messages
2,870
You could also use the fact that it is a multiple choice question to test out each answer. Remember that if \(\displaystyle \frac{a}{b}=c\) then \(\displaystyle a=b*c\).
So multiply the denominator by the expressions A-D to see which one gives you the numerator.
 
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