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Question
Expand the following, using suitable identities.
(2x + 9)(2x – 7)
Sum
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Solution
We have,
(2x + 9)(2x – 7) = (2x + 9)[(2x + (–7)]
= (2x)2 + [9 + (–7)]2x + 9 × (–7) ...[Using the identity, (x + a)(x + b) = x2 + (a + b)x + ab]
= 4x2 + 4x – 63
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Chapter 7: Algebraic Expression, Identities and Factorisation - Exercise [Page 232]
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