Question

Решите системы уравнений:
1.
y-4x=9,
2y-3x=13

2.
x+7y=10
4x+5y=-6

Answer 1

$1)\left \{ {{y-4x=9}|*(-2) \atop {2y-3x=13}} \right. \\\\+\left \{ {{-2y+8x=-18} \atop {2y-3x=13}} \right.\\ -------\\5x=-5\\\\x=-1\\\\y=9+4x=9+4*(-1)=9-4=5\\\\Otvet:\boxed{(-1;5)}$

$2)\left \{ {{x+7y=10}|*(-4) \atop {4x+5y=-6}} \right.\\\\+\left \{ {{-4x-28y=-40} \atop {4x+5y=-6}} \right.\\--------\\-23y=-46\\\\y=2\\\\x=10-7y=10-7*2=10-14=-4\\\\Otvet:\boxed{(-4;2)}$