Question

Решите систему уравнений методом сложения {2х-у=7 2х+3у=27

Answer 1

{2x-y=7       | -1
{2x+3y=27

{-2x+y= -7
{2x+3y=27

-2x+2x+y+3y= -7+27
4y=20
y=5

2x-5=7
2x=7+5
2x=12
x=6
ответ: (6; 5).

Answer 2

$\left \{ {{2x-y=7,} \atop {2x+3y=27;}} \right. \left \{ {6x-3y=21,} \atop {2x+3y=27;}} \right. \\ 8x=48, \\ x=6; \\ y=2x-7, \\ y=5.$