(x+y)^2-(x+y)^3=(x+y)^2[1-(x+y)]=(1-x-y)(x+y)^2
原式=(x+y)²[1-(x+y)] =(x+y)²(1-x-y)
解:(X+Y)^2-(X+Y)^3=(X+Y)^2(1-X-Y)
(X+Y)2-(X+Y)3设A=X+Y则A2-A3=A2(1-A)=(X+Y)2(1-X-Y)
(x+y)²-(x+y)³=(x+y)²[1-(x+y)]=(x+y)²(1-x-y)