Question

factorise ab(p^2+q^2)-pq(a^2+b^2)

Answer 1

ab (p^2+q^2)-pq (a^2+b^2)
abp^2+abq^2-pqa^2-pqb^2
ap (bp-qa)-qb (bp-qa)
(ap-qb) (bp-qa)