Question

se (x-y)² - (x+y)² = -20 entao x.y e igual a
qual a resposta??

Answer 1

Resposta:( x + y )² - ( x - y )² = 48

xy = ?

( x² + 2.x.y + y²) - ( x² - 2.x.y + y² ) = 48

x² + 2xy + y² - ( x² - 2xy + y²) = 48

x² + 2xy + y² - x² + 2xy - y²  = 48

4xy = 48

xy = 48/4

xy = 12******

Answer 2

Oie, Td Bom?!

$(x - y) {}^{2} - (x + y) {}^{2} = - 20$

$(x - y - (x + y)) \: . \: (x - y + x + y) = - 20$

$(x - y - x - y) \: . \: 2x = - 20$

$( - 2y) \: . \: 2x = - 20$

$- 2y \: . \: 2x = - 20$

$- 4xy = - 20$

$xy = \frac{ - 20}{ - 4}$

$xy = \frac{20}{4}$

$xy = 5$

Att. Makaveli1996