若2y=3-x,则-3x+9-6y=

问题描述:

若2y=3-x,则-3x+9-6y=

由2y=3-X可得X=3-2Y(1)
把(1)代入-3X+9-6Y=-3(3-2Y)+9-6Y=-9+6Y+9-6Y=0


∵2y=3-x
∴6y=9-3x
则:
-3x+9-6y
=-3x+9-(9-3x)
=-3x+9-9+3x
=0

2y=3-x
2y+x=3
-3x+9-6y
=-3(2y+x)+9
=-3*3+9
=0