Question

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

Answer 1

a²+b²-c²+2ab

Explanation:

(x-y)(x+y)=x²-y²

[(a + b) - c ][(a + b) + c )=

=(a+b)²-c²

=a²+2ab+b²-c²

=a²+b²-c²+2ab

Answer 2

`a^2+b^2-c^2+2ab`

Explanation:

`(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`

Hope this helps!