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Railways PYQCBT 1 2016

RRB NTPC · Question 29

If (x + 1/x) = 3, then find the value of (x^3 + 1/x^3) ÷ (x^2 + 1/x^2). A. 18/5 B. 26/3 C. 18/7 D. 54/5

  1. D

  2. B

  3. A

  4. C

Show answer & explanation

Answer: (D) C

Explanation

x + 1/x = 3 gives x² + 1/x² = 9 − 2 = 7 and x³ + 1/x³ = 27 − 3 × 3 = 18. The ratio is 18/7.