(x+y+z)²-(x-y-z)²

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(x+y+z)²-(x-y-z)²(x+y+z)²-(x-y-z)²(x+y+z)²-(x-y-z)²=((x+y+z)-(x-y-z))*

(x+y+z)²-(x-y-z)²
(x+y+z)²-(x-y-z)²

(x+y+z)²-(x-y-z)²
=((x+y+z)-(x-y-z))*((x+y+z)+(x-y-z))=2(y+z)*2*x=4xy+4xz

(x+y+z)²-(x-y-z)²=(x+y+z+x-y-z)(x+y+z-x+y+z)=2x*(2y+2z)=4xy+4xz

(x+y+z)²=x²+2x(y+z)+(y+z)²
(x-y-z)²=x²-2x(y+z)+(y+z)²
(x+y+z)²-(x-y-z)²=4x(y+z)