Question

qual o valor numerico de XY sendo (x-y)²=20 e x²+y²=80

Answer 1

[(x-y)^2 = 20]
[x^2 - 2xy + y^2 = 20]
[(x^2 + y^2) - 2xy = 20]
[80 - 2xy = 20]
[-2xy = -60]
xy = 30