已知2x-y=3,求4-x+1/2y

已知2x-y=3,求4-x+1/2y
已知2x-y=3,求4-x+1/2y

已知2x-y=3,求4-x+1/2y
2x-y=3得x-1/2y=3/2,所以4-x+1/2y=4-(x-1/2y)=4-3/2=5/2

（2x-y）*（-1/2）=-1.5
-x+1/2y=-1.5
4+（-1.5）=2.5
4-x+1/2y=2.5

2x-y=3
两边除以-2
-x+1/2y=-3/2
4-x+1/2y=4-3/2=5/2