\begin{cases}x-y=4\\x^2+y^2+2xy=36\end{cases}<=>\\<=>\begin{cases}x-y=4=>x=4+y\\(x+y)^2=36\end{cases}\\(4+y+y)^2=36\\(4+2y)^2=36\\4+2y=6\ ;4+2y=-6\\2y=2\ \ \ \ \ \ ;2y=-10\\y=1\ \ \ \ \ \ \ ;y=-5\\x=5\ \ \ \ \ \ \ \ x=-1\\OTBET:(5;1);(-1;-5)" alt="\begin{cases}x-y=4\\x^2+y^2=36-2xy\end{cases}<=>\begin{cases}x-y=4\\x^2+y^2+2xy=36\end{cases}<=>\\<=>\begin{cases}x-y=4=>x=4+y\\(x+y)^2=36\end{cases}\\(4+y+y)^2=36\\(4+2y)^2=36\\4+2y=6\ ;4+2y=-6\\2y=2\ \ \ \ \ \ ;2y=-10\\y=1\ \ \ \ \ \ \ ;y=-5\\x=5\ \ \ \ \ \ \ \ x=-1\\OTBET:(5;1);(-1;-5)" align="absmiddle" class="latex-formula">