已知X+Y=负4.,怎样求2分之1(X+Y)-4(X-Y)+3(X-Y)-2分之3(X+Y)+(X-y)的值

问题描述:

已知X+Y=负4.,怎样求2分之1(X+Y)-4(X-Y)+3(X-Y)-2分之3(X+Y)+(X-y)的值

2分之1(X+Y)-4(X-Y)+3(X-Y)-2分之3(X+Y)+(X-y)
=[2分之1(X+Y)-2分之3(X+Y)]+[-4(X-Y)+3(X-Y)+(X-y)]
=-(X+Y)
=-(-4)
=4