Question

Решите систему уравнений {
х − 2у = −1
3х + у = 11

Answer 1

$x = -1 +2y; \ \ x=2y-1 \\ \\ \\ 3x +y =11; \ \ \ 3 \cdot (2y-1)+y =11; \\ 6y -3 +y =11; \ \ \ 7y =11+3; \ \ 7y=14; \ \ \ y = \frac{14}{7}=2 \\ \\ \\ x=2y-1= 2\cdot 2 -1=4-1=3$


Ответ: x=3, y=2

Answer 2

$\left \{ {{x-2y=-1} \atop {3x+y=11/*2}} \right. \\ \\ \left \{ {{x-2y=-1} \atop {6x+2y=22}} \right. \\ 7x=21\\x=3\\\\18+2y=22\\2y=22-18 \\ 2y=4 \\ y=2 \\ \\ \left \{ {{x=3} \atop y=2}} \right.$