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Mathematics

If x4 - 5x2 + 4 = 0; the values of x are :

  1. 1 or 2

  2. ± 1 or ± 2

  3. -1 and 2

  4. -2, -1, 1 or 2

Quadratic Equations

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Answer

Given,

⇒ x4 - 5x2 + 4 = 0

⇒ x4 - 4x2 - x2 + 4 = 0

⇒ x2(x2 - 4) - 1(x2 - 4) = 0

⇒ (x2 - 1)(x2 - 4) = 0

⇒ x2 - 1 = 0 or x2 - 4 = 0

⇒ x2 = 1 or x2 = 4

⇒ x = 1\sqrt{1} or x = 4\sqrt{4}

⇒ x = ± 1 or x = ± 2.

Hence, Option 2 is the correct option.

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