Question

Sabendo que x + y = 12 e x - y = 8,
quanto vale x² - y2?​

Answer 1

$\left \{ {{x+y=12} \atop {x-y=8}} \right.$

$2x=20$

$x=10$

$10+y=12$

$y=12-10$

$y=2$

$x^2-y^2=10^2-2^2=100-4=96$