Question

Qual o valor de xy,sabendo que x-y=40e x²+y²=2600

Answer 1

Elevando $x-y = 40$ ao quadrado , temos :

$(x-y)^{2} = 40^{2}$

$x^{2} -2xy + y^{2} = 1600$

$( x^{2} + y^{2} )-2xy = 1600$

$2600-2xy = 1600$

$2xy = 2600-1600 = 1000$

$xy = \frac{1000}{2} = 500$