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Railways PYQCBT 1 2016

RRB NTPC · Question 65

Expand (a - 4)^3?

  1. a^3 – 12a^2 + 48a + 64
  2. a^3 – 48a^2 + 12a – 64
  3. a^3 + 12a^2 – 48a – 64
  4. a^3 – 12a^2 + 48a – 64
Show answer & explanation

Answer: (D) a^3 – 12a^2 + 48a – 64

Explanation

(a − b)³ = a³ − 3a²b + 3ab² − b³, so (a − 4)³ = a³ − 12a² + 48a − 64.