Check whether the following equation is a quadratic equation:
(x + 1)² = 2(x – 3)

The correct answer is No, this is not a quadratic equation

(x + 1)² = 2(x – 3)
LHS = (x + 1)² = x² + 2x + 1
RHS = 2(x – 3) = 2x - 6
∴ x² + 2x + 1 = 2x - 6
i.e. x² + 2x + 1 - 2x + 6 = 0
or x² + 7 = 0
Since the above equation is not of the form ax² + bx + c = 0, this is not a quadratic equation