Question

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

Answer 1

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

Explanation:

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

1. expand

(a^2 + ab + ac + ba + b^2 + bc - ca - cb - c^2)

2. rearrange,

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

3. add and subtract

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