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Question -

If a тАУ b = 4 and ab = 21, find the value of a3-b3.



Answer -

a тАУ b = 4, ab= 21
Cubing both sides,
тЗТ (a тАУA)3┬а= (4)3
тЗТ a3┬атАУb3┬атАУ 3ab (a тАУ b) = 64
тЗТ a3-i3-3├Ч21x4 = 64
тЗТ┬аa3┬атАУ 63┬атАУ 252 = 64
тЗТ┬аa3┬атАУ 63┬а= 64 + 252 =316
тИ┤ a3┬атАУb3┬а= 316

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