Question

Solve:
(a+b+c) (a+b+c) - (a-b-c) (a-b-c)

Answer 1

$(a + b + c)(a + b + c) - (a - b - c)(a - b - c) \\ = {(a + b + c)}^{2} - {(a - b - c)}^{2} \\ = [a + b + c +( a - b - c)][a + b + c - (a - b - c)] \\ =( 2a)(2b + 2c) \\ = 4ab + 4ac\\=4(ab+ac)$