x-y=4
4x+2y=-1 因为:x=4+y 所以:4(4+y)+2y=-1
16y+4y+2y=-1
22y=-1
y=-1/22
所以: x+1/22=4
x=4-1/22
x=87/22
x-y=4化为x=4+y
带入4x+2y=-1
4(4+y)+2y=-1
16+2y=-1
y=-17/6
x=7/6