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Question
If 2a - 3b = 10 and ab = 16; find the value of 8a3 - 27b3.
Sum
Solution
2a - 3b = 10
(2a - 3b)3 = (2a)3 - (3b)3 - 2(2a) (3b) (2a - 3b)
⇒ 1000 = 8a3 - 27b3 - 12(16) (10)
⇒ 8a3 - 27b3
= 1000 + 1920
= 2920.
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