# I am in dire need of assistance!!!

#### JeffM

##### Elite Member
There are at least three ways to attack this problem.

The most general is to realize that

$4^n - 1 = (2^2)^n - 1 = 2^{2n} - 1.$
Can you see the next step?

#### Subhotosh Khan

##### Super Moderator
Staff member
Do you see that (4^n -1 ) is in the form of ( a^2 - b^2) ?

Do you know that:

(a^2 - b^2) = (a + b) * (a - b)

Use those "facts" to simplify the numerator and proceed.

#### Harry_the_cat

##### Elite Member
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.