Question
Expand each of the following using suitable identities:
(3a -7b - c)2
Solution
(3a -7b - c)1
(3a - 7b - c)2 = {3a + (- 7b) + (- c)}2
= (3a)2 + (- 7b)2 + (- c)2 + 2(3a)(- 7b) + 2(- 7b)(- c) + 2(- c)(3a)
= 9a2 + 49b2 + c2 - 42ab + 14bc - 6ca
