Question

Решите систему уравнения
х+у=7,
3у-5х=5;

Answer 1

$\left \{ {{y+x=7}\atop{3y-5x=5}}\right. \\ \\ \left \{ {{x=7-y} \atop {3y-5x=5}} \right. \\ \\ 3y-5(7-y)=5 \\ \\ 3y-35+5y=5 \\ \\ 8y=5+35 \\ \\ 8y=40 \\ \\ y=5 \\ \\ x=7-y \\ \\ x=7-5=2 \\ \\ (x;y)=(2;5)$