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问题: 整式的运算 1

已知:XY=-2,X-Y=3,求(X+Y)(X-Y)-(Y*Y)+(X-Y)(X-Y)-(6X*XY-2XY*Y)的值

解答:

解方程组xy=-2,x-y=3,得到x=1,y=-2或者x=2,y=-1所以x+y=+'-1
因此,原式=(x+y)(x-y)-xy(x-y)^2-2xy(3x-y)
x=1,y=-2时,得1*3-(-2)*3^2-2(-2)(3*1+2)=41
x=2,y=-1时,得1*3-(-2)*3^2-2(-2)(3*2+1)=49