{x^2+y^2=5,{xy=2; x^2+2xy+y^2-2xy=5,(x+y)^2-2xy=5;(x+y)^2-2*2=5;(x+y)^2=9; [x+y=-3,[x+y=3; [y=-3-x,[y=3-x; [-x(3+x)=2,[x(3-x)=2; [x^2+3x+2=0,[x^2-3x+2=0;x_1=-2, x_2=-1, x_3=1, x_4=2,y_1=-1, y_2=-2, y_3=2, y_4=1. {x^2-8xy+16y^2=25,{4y^2-xy=5; {(x-4y)^2=25,{y(4y-x)=5; [x-4y=-5,[x-4y=5; -y(x- 4y)=5, Вот так думаю[5y=5,[-5y=5;y_1=1, y_2=-1; [x-4=-5,[x-4*(-1)=5;x_1=-1, x_2=1.