a) You can't use 'macro parameter character #' in math mode\begin{gather} f(x)=\sqrt{ x^{2}-4x+4 } \\ g(x)=|x-2| \\ \\ f(x)=\sqrt{ (x-2)^{2} } &=\\ |x-2| \\ \\ \underline{\underline{ g(x)=f(x) }} \end{gather} $$ # b) $L=\mathbb{R}$