方程式群x-y=m,x+y=0m-8の解满足x+2y=4,則m=?

方程式群x-y=m,x+y=0m-8の解满足x+2y=4,則m=?

m=4
x-y=m1
x+y m-82
①+②
2xm-8
①-②
2y=2m-8
x+2y=4
2m-4+2(m-4)=4
m=4