make y the subject of the formula x=2^y (were 2^y mean 2 to the power Y)

make y the subject of the formula x=2^y (were 2^y mean 2 to the power Y)

Take the log base 2 of both side.


\log _2 x = \log_2 (2^y)


and recall that \log _ a (a^b) = b

2^y=x \to \log_2 {x}=y
note: \log_2 {x}=\frac {\log_{10} {x}}{\log_{10} 2}
exaple: 3^2=9 \to \log_3 {9}=2