Question

已知X+Y=—4,怎么样求1/2(X+Y)---4(X-Y)+3(X-Y)--3/2(X+Y)+(X--Y)的值

Answer 1

1/2(X+Y)-4(X-Y)+3(X-Y)-3/2(X+Y)+(X-Y)
=1/2(X+Y)-3/2(X+Y)-4(X-Y)+3(X-Y)+(X-Y)
=(X+Y)(1/2-3/2)+(X-Y)(-4+3+1)
=(X+Y)(-2/2)+(X-Y)(0)
=-(X+Y)+0
=-(-4)
=4

Answer 2

1/2(X+Y)---4(X-Y)+3(X-Y)--3/2(X+Y)+(X--Y）其中(X-Y)可以去掉。其中---4(X-Y)+3(X-Y）)+(X--Y）=0 所以答案是1/2(X+Y)--3/2(X+Y）=-)--(X+Y）=4