Question

Найдите решение системы уравнений
{x + y = 7
{9y - 2x = -26

Answer 1

$\displaystyle\bf\\\left \{ {{x+y=7} \atop {9y-2x=-26}} \right. \\\\\\\left \{ {{x+y=7 \ |\cdot 2} \atop {-2x+9y=-26}} \right. \\\\\\+\left \{ {{2x+2y=14} \atop {-2x+9y=-26}} \right. \\----------\\11y=-12\\\\y=-\frac{12}{11} =-1\frac{1}{11} \\\\\\x=7-y=7-\Big(-1\frac{1}{11} \Big)=7+1\frac{1}{11} =8\frac{1}{11} \\\\\\Otvet \ : \ \Big(8\frac{1}{11} \ ; \ -1\frac{1}{11} \Big)$