化简求值:【(x+Y)(X-Y)-(X-Y)的平方+2Y(2-Y)】除4Y,其中X=1 Y=2

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化简求值:【(x+Y)(X-Y)-(X-Y)的平方+2Y(2-Y)】除4Y,其中X=1 Y=2
化简求值:【(x+Y)(X-Y)-(X-Y)的平方+2Y(2-Y)】除4Y,其中X=1 Y=2

化简求值:【(x+Y)(X-Y)-(X-Y)的平方+2Y(2-Y)】除4Y,其中X=1 Y=2
(x-y)[(x+y)+x-y]+4y-2y^2
=2x(x-y)+4y-2y^2
=2[x^2-xy+2y-y^2]
所以 =2[1-2+4-4]/8=-1/4

[(x+Y)(X-Y)-(X-Y)的平方+2Y(2-Y)]除4Y={(X-Y)[X+Y-(X-Y)]+2Y(2-Y)}/4=2Y[(X-Y)+(2-Y)]/4Y=(X+2-2Y)/2 带入X,Y,即得-0.5