Discussion

Explanation:

For an equation to be called quadratic, the highest power of the variable should be 2.

Equations in options (a) and (c) are not quadratic equations because in 
(a) highest power of x is fractional and in 
(c) highest power of x is 4.

For option (b), (x – 2)(x + 5) = x² + 4

⇒ x² + 5x – 2x -10 = x² + 4

⇒ 3x – 14 = 0

which is not a quadratic equation but a linear equaiton.

For option (d), (x + 3)(2x – 1) = x² + 7

⇒ 2x² + 6x - x – 3 = x² + 7

⇒ x² + 5x – 10 = 0

which is clearly a quadratic equation.

Hence, option (d).

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