Factorize:

15b² – 3bx2 – 5b + x²

Given 15b² – 3bx2 – 5b + x² = (3b×5b – 3b×x² + ( – 1)× 5b + x² )

Taking 3b common from 1^st and 2^nd term and ( – 1) from 3^rd and 4^th,

15b² – 3bx2 – 5b + x²= 3b(5b – x²) + ( – 1)(5b – x²)

⇒ 15b² – 3bx2 – 5b + x²= (5b – x²) (3b – 1)