Question

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

Answer 1

This is in the form of a^2 - b^2 = (a + b) * (a - b)

Thus,

(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

Thus, (a + b + c)^2 - (a - b - c)^2 = 4ab + 4ac.