(2a+b-c)(c+b+2a)-(2a+c-b)²

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(2a+b-c)(c+b+2a)-(2a+c-b)²

(2a+b-c)(c+b+2a)-(2a+c-b)²
(2a+b-c)(c+b+2a)-(2a+c-b)²

(2a+b-c)(c+b+2a)-(2a+c-b)²
(2a+b-c)(c+b+2a)-(2a+c-b)²
=(2a+b)²-c²-(2a+c-b)²
=[(2a+b)+(2a+c-b)][(2a+b)-(2a+c-b)]-c²
=(2a+b+2a+c-b)(2a+b-2a-c+b)-c²
=(4a+c)(2b-c)-c²
=8ab-4ac+2bc-c²-c²
=8ab-4ac+2bc-2c²