Factorize the following expressions:

p² + pq + pr + qr

= p² + pq + pr + qr
Taking p common in p² + pq

we get,

= p(p + q) + pr + qr
Taking r common in pr + qr
we get,
= p(p + q) + r(p + q)

Taking (p + q) common in both the terms

we get,
= (p + q)(p + r)
p² + pq + pr + qr = (p + q)(p + r)