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If a^(2) + (1)/(a^(2))= 47 and a ne 0, f...

If `a^(2) + (1)/(a^(2))= 47 and a ne 0`, find:
`a^(3) + (1)/(a^(3))`

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To solve the problem, we need to find the value of \( a^3 + \frac{1}{a^3} \) given that \( a^2 + \frac{1}{a^2} = 47 \) and \( a \neq 0 \). ### Step-by-step Solution: 1. **Start with the given equation:** \[ a^2 + \frac{1}{a^2} = 47 \] 2. **Use the identity for \( a + \frac{1}{a} \):** We know that: \[ \left(a + \frac{1}{a}\right)^2 = a^2 + 2 + \frac{1}{a^2} \] Rearranging gives us: \[ a^2 + \frac{1}{a^2} = \left(a + \frac{1}{a}\right)^2 - 2 \] Substituting the value we have: \[ 47 = \left(a + \frac{1}{a}\right)^2 - 2 \] Adding 2 to both sides: \[ \left(a + \frac{1}{a}\right)^2 = 49 \] 3. **Take the square root:** \[ a + \frac{1}{a} = \pm 7 \] 4. **Use the identity for \( a^3 + \frac{1}{a^3} \):** We know that: \[ a^3 + \frac{1}{a^3} = \left(a + \frac{1}{a}\right)^3 - 3\left(a + \frac{1}{a}\right) \] Substituting \( a + \frac{1}{a} = 7 \) (we can ignore -7 as it will yield the same result): \[ a^3 + \frac{1}{a^3} = 7^3 - 3 \times 7 \] 5. **Calculate \( 7^3 \) and \( 3 \times 7 \):** \[ 7^3 = 343 \] \[ 3 \times 7 = 21 \] 6. **Substitute and simplify:** \[ a^3 + \frac{1}{a^3} = 343 - 21 = 322 \] ### Final Answer: \[ a^3 + \frac{1}{a^3} = 322 \]
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ICSE-EXPANSIONS-Exercise 4(B)
  1. Find the cube of: 3a - (1)/(a) (a ne 0)

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  2. If a^(2) + (1)/(a^(2))= 47 and a ne 0, find: a+ (1)/(a)

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  3. If a^(2) + (1)/(a^(2))= 47 and a ne 0, find: a^(3) + (1)/(a^(3))

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  4. If a^(2) + (1)/(a^(2)) = 18 and a ne 0, find: a- (1)/(a)

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  5. If a^(2) + (1)/(a^(2)) = 18 and a ne 0, find: a^(3)- (1)/(a^(3))

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  6. If a + (1)/(a)= p and a ne 0, then show that: a^(3) + (1)/(a^(3))= p (...

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  7. If a + 2b= 5, then show that: a^(3) + 8b^(3) + 30ab = 125

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  8. If (a + (1)/(a))^(2) = 3 and a ne 0, then show that: a^(3) + (1)/(a^(3...

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  9. If a + 2b + c= 0, then show that: a^(3) + 8b^(3) + c^(3)= 6abc

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  10. Use property to evaluate: 13^(3) + (-8)^(3) + (-5)^(3)

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  11. Use property to evaluate: 7^(3) + 3^(3) + (-10)^(3)

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  12. Use property to evaluate: 9^(3) -5^(3) - 4^(3)

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  13. Use property to evaluate: 38^(3) + (-26)^(3) + (-12)^(3)

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  14. If a ne 0 and a - (1)/(a)= 3, find : a^(2) + (1)/(a^(2))

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  15. If a ne 0 and a - (1)/(a)= 3, find : a^(3)- (1)/(a^(3))

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  16. If a ne 0 and a - (1)/(a)= 4, find a^(2) + (1)/(a^(2))

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  17. If a ne 0 and a - (1)/(a)= 4, find a^(4) + (1)/(a^(4))

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  18. If a ne 0 and a - (1)/(a)= 4, find a^(3)- (1)/(a^(3))

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  19. If x ne 0 and x + (1)/(x) = 2, then show that: x^(2)+ (1)/(x^(2))= x^(...

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  20. If 2x- 3y= 10 and xy= 16, find the value of 8x^(3)- 27y^(3)

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