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Question
Expand (2a + 5)3
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Solution
(2a + 5)3
Comparing (2a + 5)3 with (a + b)3 we have a = 2a, b = 5
(a + b)3 = a3 + 3a2b + 3ab2 + b3
= (2a)3 + 3(2a)25 + 3(2a)52 + 53
= 23a3 + 3(22a2)5 + 6a(25) + 125
= 8a3 + 60a2 + 150a + 125
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