Question

Решите систему 5x+8y=-1
x+2y=4

Answer 1

$\left \{ {{5x+8y=-1} \atop {x+2y=4}} \right. \\\\ \left \{ {{5x+8y=-1} \atop {x=4-2y}} \right. \\\\ \left \{ {{5(4-2y)+8y=-1} \atop {x=4-2y}} \right. \\\\ \left \{ {{20-10y+8y=-1} \atop {x=4-2y}} \right. \\\\ \left \{ {{20-2y=-1} \atop {x=4-2y}} \right. \\\\ \left \{ {{-2y=-1-20} \atop {x=4-2y}} \right. \\\\ \left \{ {{-2y=-21} \atop {x=4-2y}} \right. \\\\ \left \{ {{2y=21} \atop {x=4-21}} \right. \\\\ \left \{ {{y=\frac{21}{2}} \atop {x=-17}} \right.$

$\left \{ {{x=-17} \atop {y=-10.5}} \right.$

Ответ: $(-17;\ -10.5)$