Railways PYQCBT 1 2016

RRB NTPC · Question 63

If (a + c + 1) = 0, then find the value of (a^3 + c^3 + 1 – 3ac)

  1. -1

  2. 1

  3. 2

  4. 0

Show answer & explanation

Answer: (D) 0

Explanation

Use the identity x³ + y³ + z³ − 3xyz = (x + y + z)(x² + y² + z² − xy − yz − zx). With x = a, y = c and z = 1, the expression a³ + c³ + 1 − 3ac has the factor a + c + 1, which is 0. So the value is 0.