Question

Решите систему уравнений способом подстановки

Answer 1

$\left \{ {{3(x+y)+1=x+4y} \atop {7-2(x-y)=x-8y}} \right. \\ \\ \left \{ {{3x+3y+1=x+4y} \atop {7-2x+2y=x-8y}} \right. \\ \\ \left \{ {{2x-y=-1} \atop {-3x+10y=-7}} \right. \\ \\ y=2x+1 \\ \\ -3x+10(2x+1)=-7 \\ \\ -3x+20x+10=-7 \\ \\ 17x=-17 \\ \\ x=-1 \\ \\ y=2 * (-1)+1=-1$

Ответ: (-1; -1)