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Railways PYQCBT 1 2020

RRB NTPC · Question 36

(x - y)^3 + (y - z)^3 + (z - x)^3 = ?

  1. 3xyz

  2. 3(x - y)(y - z)(z - x)

  3. (x + y + z)(x^2 + y^2 + z^2)

  4. (x - y)(y - z)(z - x)

Show answer & explanation

Answer: (B) 3(x - y)(y - z)(z - x)

Explanation

If a + b + c = 0 then a³ + b³ + c³ = 3abc. Here (x − y) + (y − z) + (z − x) = 0, so the sum = 3(x − y)(y − z)(z − x).