Question

x+2y=0 3x-7y=-13
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Answer 1

ОТвет: (-2;1)

Решение:
из первого уравнения найдём х и подставим во второе$\left \{ {{x+2y=0} \atop {3x-7y=-13}} \right. \left \{ {{x=-2y} \atop {3(-2y)-7y=-13}} \right. \left \{ {{x=-2y} \atop {-6y-7y=-13}} \right. \left \{ {{x=-2y} \atop {y=-13:(-13)}} \right. \left \{ {{x=-2*1} \atop {y=1}} \right. \{ {{x=-2} \atop {y=1}} \right.$

Answer 2

$\displaystyle\bf\\\left \{ {{x+2y=0} \atop {3x-7y=-13}} \right. \\\\\\\left \{ {{x=-2y} \atop {3\cdot(-2y)-7y=-13}} \right. \\\\\\\left \{ {{x=-2y} \atop {-6y-7y=-13}} \right. \\\\\\\left \{ {{x=-2y} \atop {-13y=-13}} \right. \\\\\\\left \{ {{x=-2\cdot 1} \atop {y=1}} \right. \\\\\\\left \{ {{x=-2} \atop {y=1}} \right.\\\\\\Otvet \ : \ (-2 \ ; \ 1)$