MCQ
(x + y)3 - (x - y)3 can be factorized as:
  • A
    2x(3x2 + y2)
  • B
    2y(3y2 + x2)
  • C
    2y(3x2 + y2)
  • D
    2x(x2 + 3y2)

Answer

  1. 2y(3x2 + y2)
    Solution:
    Put a = x + y and b = x - y, then
    (x + y)3 - (x - y)3 = a3 - b3
    = (a − b) (a2 + b2 + ab)
    = (x + y - x + y) [(x + y)2 + (x - y)2 + (x - y) (x+y)]
    =2y[2(x2 + y2) + (x2 - y2)]
    =2y[3x2 + y2]

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