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Question
Simplify:
(a + b)3 + (a - b)3
Solution
(a + b)3 + (a - b)3
= a3 + b3 + 3ab (a + b) + a3 - 3ab (a - b) - b3
= a3 + b3 + 3a2b + 3ab2 + a3 - 3a2b + 3ab2 - b3
= 2a3 + 6ab2.
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