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Mathematics

Which of the following is not a quadratic equation :

  1. 2x2 = 3x - 5

  2. (2x - 1)(x - 1) = 2x2 - 7x + 2

  3. (2x - 1)(x + 2) = (x - 1)(x + 1)

  4. (x + 1)3 = x3 + 2x + 2

Quadratic Equations

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Answer

On solving eq. 2 i.e. (2x - 1)(x - 1) = 2x2 - 7x + 2 we get,

⇒ 2x2 - 2x - x + 1 = 2x2 - 7x + 2

⇒ 2x2 - 2x2 - 2x - x + 7x + 1 - 2 = 0

⇒ 4x - 1 = 0

We know that an equation in the form ax2 + bx + c = 0 (with a ≠ 0) is considered a quadratic equation. In the equation 4x - 1 = 0, a = 0 hence it is not a quadratic equation.

Hence, Option 2 is the correct option.

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