(x+3)(x-3)-(x+3)ˇ2 (xy+z)(-xy+z) (x+2y-1)(x-2y+1)是(x+3)(x-3)-(x+3)ˇ2 (x+2y-1)(x-2y+1)(xy+z)(-xy+z)这样的

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(x+3)(x-3)-(x+3)ˇ2 (xy+z)(-xy+z) (x+2y-1)(x-2y+1)是(x+3)(x-3)-(x+3)ˇ2 (x+2y-1)(x-2y+1)(xy+z)(-xy+z)这样的
(x+3)(x-3)-(x+3)ˇ2 (xy+z)(-xy+z) (x+2y-1)(x-2y+1)
是(x+3)(x-3)-(x+3)ˇ2
(x+2y-1)(x-2y+1)
(xy+z)(-xy+z)这样的

(x+3)(x-3)-(x+3)ˇ2 (xy+z)(-xy+z) (x+2y-1)(x-2y+1)是(x+3)(x-3)-(x+3)ˇ2 (x+2y-1)(x-2y+1)(xy+z)(-xy+z)这样的
(x+3)(x-3)-(x+3)ˇ2
=x²-9-(x²+6x+9)
=-6x-18
(xy+z)(-xy+z)
=z²-(xy)²
=z²-x²y²
(x+2y-1)(x-2y+1)
=x²-(2y-1)²
=x²-4y²+4y-1

(x+3)(x-3)-(x+3)ˇ2=(x²-9)-(x²+6x+9)=-6x-18
(x+2y-1)(x-2y+1)=(x+2y-1)[x-(2y-1)]=x²-(2y-1)²
(xy+z)(-xy+z)=-(xy+z)(xy-z)=-x²y²-z²