Question

Add p(p-9,9 (9-r) and r (r-p)​

Answer 1

p(p−q),q(q−r),r(r−p)

⇒p(p−q)+q(q−r)+r(r−p)

⇒p2 −pq+q 2 −qr+r 2−rp

Thus the sum =p 2+q 2 +r 2−pq−qr−pr