Check whether the following are quadratic equations:
(x + 1)² = 2(x – 3)

L.H.S. = (x + 1)² = x² + 2x + 1
R.H.S. = 2(x – 3) = 2x –6
∴ 6x² + 2x + 1 = 2x - 6
⇒ x² + 2x + 1–2x + 6 = 0
⇒ x²+ 7 = 0
∵ It is of the form ax² + bx + c = 0, where a = 1,b = 0, c = 7.
Hence, the given equation is a quadratic equation.