Question

$x - y = 4 \\ x + y = 20$
resposta com contas ​

Answer 1

Resposta:

$x - y = 4 \\ x + y = 20 \\ \\ x = 4 + y \\ 4 + y + y = 20 \\ 4 + 2y = 20 \\ 4 + 2y - 20 = 0 \\ 2y - 16 = 0 \\ 2y = 16 \div (2) \\ y = 8 \\ \\ x = 4 + y \\ x = 4 + 8 \\ x = 12 \\ \\ (x.y) = (12.8)$