Which of the following is a quadratic equation?


The standard form of a quadratic equation is given by,

ax2 + bx + c = 0, a ≠ 0


A. Given, x2 + 2x + 1 = (4 - x)2 + 3


x2 + 2x + 1 = 16 - 8x + x2 + 3


10x – 18 = 0


which is not a quadratic equation.


B. Given, -2x2 = (5 - x) (2x – )


-2x2 = 10x - 2x2 – 2 +


52x – 10 = 0


which is not a quadratic equation.


C. Given, (k + 1) x2 + = 7, where k = -1


(-1 + 1) x2 + = 7


3x – 14 = 0


which is not a quadratic equation.


D. Given, x3 - x2 = (x - 1)3


x3 - x2 = x3 - 3x2 + 3x - 1


2x2 - 3x + 1 = 0


which represents a quadratic equation.

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