解方程组6(x-y)-7(x+y)=21 2(x-y)-5(x+y)=-1

问题描述:

解方程组6(x-y)-7(x+y)=21 2(x-y)-5(x+y)=-1

①6(x-y)-7(x+y)=21;.
②2(x-y)-5(x+y)=-1
①-3②得x+y=3,带入①中,得x-y=7
x=5,y=-2