Factories:

ab² – bc² – ab + c²

ab² – bc² – ab + c²

Let’s first arrange the terms in a suitable form;

ab² – bc² – ab + c²

= ab² – ab – bc² + c²

= (ab² – ab) – (bc² - c²)

= ab(b – 1) – c²(b - 1)

= (b – 1)(ab – c²)

So we get,

ab² – bc² – ab + c² = (b – 1)(ab – c²)