解方程组6(x-y)-7(x+y)=21 2(x-y)-5(x+y)=-1

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解方程组6(x-y)-7(x+y)=212(x-y)-5(x+y)=-1解方程组6(x-y)-7(x+y)=212(x-y)-5(x+y)=-1解方程组6(x-y)-7(x+y)=212(x-y)-5

解方程组6(x-y)-7(x+y)=21 2(x-y)-5(x+y)=-1
解方程组6(x-y)-7(x+y)=21 2(x-y)-5(x+y)=-1

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