Question

Решите систему уравнений: {2x+y=9 5x+2y=27

Answer 1

$2x + y = 9 \\ 5x + 2y = 27 \\ \\y = 9 - 2x \\ 5x + 2(9 - 2x) = 27 \\ \\ 5x + 2(9 - 2x) = 27 \\ 5x + 18 - 4x = 27 \\ x = 27 - 18 \\ x = 9 \\ \\ y = 9 - 2x = 9 - 2 \times 9 = 9 - 18 = - 9 \\ \\ Ответ:(9 \: ; \: - 9)$