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Factorise: 9(a − 2)^2 − 16(a + 2)^2

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Question

Factorise: 

9(a − 2)2 − 16(a + 2)2

Sum
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Solution

9(a − 2)2 − 16(a + 2)2

= 3(a − 2)2 − [4(a + 2)]2

= [3(a − 2) + 4(a + 2)][3(a − 2) − 4(a + 2)]    ...[∵ a2 − b2 = (a + b)(a − b)]

= [3a − 6 + 4a + 8] [3a − 6 − 4a − 8]

= (7a + 2)(−a − 14)

= −(7a + 2)(a + 14)

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Method of Factorisation : Difference of Two Squares
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Chapter 5: Factorisation - Exercise 5 (C) [Page 72]

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Selina Concise Mathematics [English] Class 9 ICSE
Chapter 5 Factorisation
Exercise 5 (C) | Q 8 | Page 72
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