Question

sabendo que x²+y²=17 e (x+y)²=25 qual e o valor de xy ?

Answer 1

A resposta final é x = ±4, y = ±1

Answer 2

$x^{2} + y^{2} =17$

$(x+y)^{2} =25$ ⇒ $x^{2} +2xy+ y^{2} =25$

$2xy+ x^{2} +y^{2} =25$

$2xy+ 17 =25$

$2xy =25-17$

$2xy =8$

$xy = \dfrac{8}{2}$

$xy = 4$