Question

Simplify by using formula :
(a + b - c) (a - b + c)

Answer 1

(a + b - c) (a - b + c)
= (a + b - c) [a - (b - c)]
= (a)² - (b - c)²
(using identity : (a + b) (a - b) = a² - b²)
= a² - (b² + c² - 2bc)
= a² - b² - c² + 2bc.