(x+y+z)(-x-y+z)
=z^2-(x+y)^2
=z^2-x^2-2xy-y^2
(x+y+z)(-x-y+z)
=z^2-(x+y)^2
=z^2-x^2-2xy-y^2❤
(x+y+z)(-x-y+z)
=(z+x+y)(z-x-y)
=[z+(x+y)][z-(x+y)]
=z^2-(x+y)^2
(x+y+z)(-x-y+z)=(z+(x+y))(z-(x+y))= z^2-(x+y)^2= z^2 -(x^2 +2*x*y+y^2)
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