Дам 20 балов.

Решите задачу:

$\left \{ {{x^2+y^2=25} \atop {xy=12}} \right. \; \left \{ {{x^2+y^2=25} \atop {2xy=24}} \right. \; \left \{ {{x^2+2xy+y^2=49} \atop {xy=12}} \right. \; \left \{ {{(x+y)^2=49} \atop {xy=12}} \right. \\\\\\ \left \{ {{x+y=7} \atop {xy=12}} \right. \; \; \; ili\; \; \; \left \{ {{x+y=-7} \atop {xy=12}} \right. \\\\ \left \{ {{x=4,x=3} \atop {y=3,y=4}} \right. \; \; \; ili\; \; \; \left \{ {{x=-4,x=-3} \atop {y=-3,y=-4}} \right. \\\\Otvet:\; \; (4,3),\; (3,4),\; (-4,-3),\; (-3,-4).$