Although this is not actually homework, it's an exercise from the book;
I want to rewrite the variance,
\begin{equation*} var[f]=E[(f(x)-E[f(x)])^2] \end{equation*}
as
\begin{equation*} E[f(x)^2]-E[f(x)]^2. \end{equation*}
I'm not sure how it reduces, and it has had me stumped for a while. The answer would be nice. Any insight [a brief, yet, interesting explanation] would be great.
Thanks in advance