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Question
Simplify:
(3xy − 2ab)3 − (3xy + 2ab)3
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Solution
It is known that,
a3 − b3 = (a − b)(a2 + ab + b2)
(3xy − 2ab)3 − (3xy + 2ab)3
= {(3xy − 2ab) − (3xy + 2ab)} {(3xy − 2ab)2 + (3xy + 2ab)(3xy − 2ab) + (3xy + 2ab)2}
= (− 4ab) (9x2y2 + 4a2b2 − 12abxy + 9x2y2 + 4a2b2+ 12abxy + 9x2y2 − 4a2b2)
= (− 4ab)(27x2y2 + 4a2b2)
= − 108x2y2ab − 16a3b3
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\[\frac{a^2 + 10a + 21}{a^2 + 6a - 7} \times \frac{a^2 - 1}{a + 3}\]
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8p3 −\[\frac{27}{p^3}\]
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