# Math Help - Logarithm

1. ## Logarithm

This was found in my book:

$\log_4 y=\frac{\log_2 4}{\log_2 y}$

Why the answer is not $\frac{\log_2 y}{\log_2 4}$?

Is there another formula to change base or my book is wrong?

2. Originally Posted by cloud5
This was found in my book:

$\log_4 y=\frac{\log_2 4}{\log_2 y}$

Why the answer is not $\frac{\log_2 y}{\log_2 4}$?

Is there another formula to change base or my book is wrong?
I have no idea, as far as I know your book is wrong. The correct answer is the one you pointed out although $\log_2(4) = 2$ so it can be simplified