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Question
Expand (2x – 4y)3
Sum
Solution
(2x – 4y)3
Comparing (2x – 4y)3 with (a – b)3 we have a = 2x and b = 4y
(a – b)3 = a3 – 3a2b + 3ab2 – b3
(2x – 4y)3 = (2x)3 – 3(2x)2(4y) + 3(2x)(4y)2 – (4y)3
= 23x3 – 3(22x2)(4y) + 3(2x)(42y2) – (43y3)
= 8x3 – 48x2y + 96xy2 – 64y3
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Chapter 3: Algebra - Exercise 3.3 [Page 91]
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