Question

Factorise x²-2xy-y²-z²

Answer 1

(x^2−2xy+y^2)−z^2

⇒[x(x−y)−y(x−y)]−z^2

⇒(x−y)(x−y)−z^2

⇒(x−y)^2−z^2

⇒[(x−y)+z][(x−y)−z]

⇒(x−y+z)(x−y−z)