Question

unitau-sp 2018 se 2x - y =20 e x + 2y = 7 , então x +y e

Answer 1

Resposta:

$2x - y = 20 \\ x + 2y = 7 \\ \\ x = 7 - 2y \\ 2(7 - 2y) - y = 20 \\ 14 - 4y - y = 20 \\ - 5y = 20 - 14 \\ y = - \frac{6}{5} \\ \\ x = 7 + 2 \frac{6}{5} \\ x = \frac{47}{5} \\ \\ x + y = - \frac{6}{5} + \frac{47}{5} = \frac{41}{5}$