9.1.11 Double integrals

Problem: Make a replacement of variables in the double integral: \[ G:\left\{\begin{array}{l} y=x \\ x^{2}+y^{2}=9 \\ x y=4(x>0, y \geq x) \end{array},\left\{\begin{array}{l} u=x^{2}+y^{2}-9 \\ v=x y-4 \end{array} .\right.\right. \]