Question

x+y = 20 x.y = 80 calcule o valor de x²+y²

Answer 1

$x+y=20\\ (x+y)^2=400\\ x^2+y^2+2xy=400\\ \\ Mas \ xy=80\\ \\ x^2+y^2+2.80=400\\ \\ x^2+y^2=400-160\\ \\ x^2+y^2=240$