Question

solve (a+b+c) (a+b-c)

Answer 1

This (a+b)²-(c)²
(a+b)²=a²+b²+2ab
(a+b)²-(c)²=a²+b²+2ab-c²

Hope this helps you.

Answer 2

(a+b+c).(a+b-c)
a^2+ab+ac+ab+b^2+bc-ac-bc-c^2
a^2+b^2-c^2+2ab

this is the answer