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Question
Expand the following:
(3a – 5b – c)2
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Solution
(3a – 5b – c)2
= (3a)2 + (–5b)2 + (–c)2 + 2(3a)(–5b) + 2(–5b)(–c) + 2(–c)(3a) ...[Using identity, (a + b + c)2 – a2 + b2 + c2 + 2ab + 2bc + 2ca]
= 9a2 + 25b2 + c2 – 30ab + 10bc – 6ac
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