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Solve the given question: |
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Answer» Given, y² + 1/y² = 23⇒ (y + 1/y)² - (2 × y × 1/y) = 23⇒ (y + 1/y)² - 2 = 23⇒ (y + 1/y)² = 23 + 2⇒ (y + 1/y)² = 25⇒ y + 1/y = - 5,where we TAKE the negative value only.∴ y³ + 1/y³= (y + 1/y)³ - (3 × y × 1/y)(y + 1/y)= (- 5)³ - {3 × (- 5)}= - 125 + 15= - 110Identity rule :a³ + b³ = (a + b)³ - 3AB(a + b) |
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