How to show that $\left(\frac{y}{y-1}\right)^y = \left( 1 + \frac 1{y-1}\right)^y $ I need to show

\[\left(\frac{y}{y-1}\right)^y = \left( 1 + \frac 1{y-1}\right)^y \]

I cannot understand how they made this step! Can someone explain how this works?

We have
\[
\frac y{y-1} = \frac{y-1+1}{y-1} = \frac{y-1}{y-1} + \frac 1{y-1} = 1 + \frac 1{y-1}. \]
