Q9 of 65 Page 141

Let us factorise the following algebraic expressions:

p3 (q – r)3 + q3 (r – p)3 + r3 (p – q)3

p3 (q – r) 3 + q3 (r – p) 3 + r3 (p – q) 3


(pq – pr) 3 + (qr – pq) 3 + (pr – qr) 3


Let us consider pq – pr = a, qr – pq = b, pr – qr = c


a + b + c = pq – pr + qr – pq + pr – qr = 0


Since a + b + c = 0, hence


a3 + b3 + c3 = 3abc


p3 (q – r) 3 + q3 (r – p) 3 + r3 (p – q) 3 = 3pqr(q - r) (r – p) (p – q)


3pqr (q - r) (r – p) (p – q)


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