Question

Factorise.

(x² − 2xy + y²) − z²

Answer 1

(x² − 2xy + y²) − z²

Using the identity (a − b)² = a² − 2ab + b² 

= (x − y)² − z²

Using the identity a² − b² = (a − b) (a + b)

= (x − y − z) (x − y + z)

= [a² − b² = (a − b) (a + b)]