Question

Найдите решение системы уравнений способом подстановки: 1) 2*(х+у)-х=-6 3х-(х-у)=0 2) 3*(х+2у)-у=27 4*(х+у)-3х=23

Answer 1

1. $left { {{2(x+y)-x=-6} atop {3x-(x-y)=0}} right.\left { {{2x+2y-x=-6} atop {3x-x+y=0}} right.\left { {{x+2y=-6} atop {2x+y=0}} right.\left { {{x=-2y-6} atop {2(-2y-6)+y=0}} right.\left { {{x=-2y-6} atop {-4y-12+y=0}} right.\left { {{x=-2y-6} atop {-3y=12}} right.\left { {{x=-2y-6} atop {y=-4}} right.\left { {{x=2} atop {y=-4}} right.$

2. $left { {{3(x+2y)-y=27} atop {4(x+y)-3x=23}} right.\left { {{3x+6y-y=27} atop {4x+4y-3x=23}} right.\left { {{3x+5y=27} atop {x+4y=23}} right.\left { {{3x+5y=27} atop {x=23-4y}} right.\left { {{3(23-4y)+5y=27} atop {x=23-4y}} right.\left { {{69-12y+5y=27} atop {x=23-4y}} right.\left { {{7y=42} atop {x=23-4y}} right.\left { {{y=6} atop {x=-1}} right.$