MCQ
The factors of x4 + x2 + 25 are:
  • A
    (x2 + 3x + 5)(x2 - 3x + 5)
  • B
    (x2 + 3x + 5)(x2 + 3x − 5)
  • C
    (x2 + x +5)(x2 - x + 5)
  • D
    None of these.

Answer

  1. (x2 + 3x + 5)(x2 - 3x + 5)
    Solution:
    For making perfect square to x4 + x2 + 25
    We add +10x2 and -10x2 to it.
    = x4 + x2 + 25
    = x4 + x2 + 25 + 10x2 - 10x2
    = [x4 + 10x2 + 25] - 9x2
    = (x2 + 5)2 + (3x)2
    = [(x2 + 5) + 3x][(x2 + 5) - 3x]
    = (x2 + 3x + 5)(x2 - 3x + 5)
    Hence, correct option is (a).

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