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Mathematics

Which of the following is a quadratic equation?

  1. x2 - 2x2\sqrt{x} + 7 = 0

  2. 2x2 - 5x = (x - 1)2

  3. x1x=2x2x - \dfrac{1}{x} = 2x^{2}

  4. x2 + 1x2\dfrac{1}{x^{2}} = 2

Quadratic Equations

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Answer

Solving,

⇒ 2x2 - 5x = (x - 1)2

⇒ 2x2 - 5x = [(x)2 + (1)2 - 2 × x × 1]

⇒ 2x2 - 5x = x2 + 1 - 2x

⇒ 2x2 - 5x - x2 - 1 + 2x = 0

⇒ 2x2 - x2 - 5x + 2x - 1 = 0

⇒ x2 - 3x - 1 = 0

The highest power of equation is 2 and it's equivalent to ax2 + bx + c = 0 . Hence the equation is a quadratic equation.

Hence, option 2 is the correct option.

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