$4\mathrm{.}9.$ Let $fin{C}_L^{1,1}(R^m),$ and let $Ain{R}^{mn},bin{R}^m.$ Show that the function $g$:$R^{n}R$ defined by $g(x)=f(Ax+b)$ satisfies $gin{C}_{\text{t}\text{i}\text{l}\text{d}\text{e}(L)}^{1,1}(R^n),$ where tilde$(L)=||A|{|}^{2}L.$