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(a - 2b)3
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Using the formula,
(x - y)3 = x3 - y3 - 3x2y + 3xy2
= a3 - (2b)3 - 3 x (a)2x (2b) + 3 x (a) x (2b)2
= a3 - 8b3 - 6a2b + 12ab2
Hence, (a - 2b)3 = a3 - 8b3 - 6a2b + 12ab2
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Evaluate using expansion of (a + b)2 or (a - b)2 :
(i) (208)2
(ii) (92)2
(iii) (9.4)2
(iv) (20.7)2
(2a + b)3
(3x - 2y)3
(x + 5y)3