Question

решите систему уравнений

x-y=9
2x-y=3

Answer 1

$\left \{ {{x-y=9} \atop {2x-y=3}} \right. \left \{ {{x-y=9} \atop {-2x+y=-3}} \right.\\ \\-x=6 \\-1*(-x)=-1*6 \\x=-1*6 \\x=-6\\ \\2*(-6)-y=3 \\-12-y=3 \\-12-y=3 \\-y=3+12 \\-y=15 \\y=-15 \\(x,y)=(-6,-15)$