已知4[1-2(x+y)]+2[-(x+y)-5]=-14(x+y),求3x+3y的值.

已知4[1-2(x+y)]+2[-(x+y)-5]=-14(x+y),求3x+3y的值.
已知4[1-2(x+y)]+2[-(x+y)-5]=-14(x+y),求3x+3y的值.

已知4[1-2(x+y)]+2[-(x+y)-5]=-14(x+y),求3x+3y的值.
设Z=X+Y
4(1-2Z)+2(-Z-5)=-14Z
解得Z=0.25
3X+3Y=3Z=3(0.25)=0.75

4.5

3X+3Y=3

4—8（x+y)—2（x+y)—10=—14（x+y)
4(x+y)=6
x+y=2/3
3x+3y=3(x+y)=3*2/3=2