Examine whether the following equations are quadratic equations or not:

(2x + 1)(2x — 1) = (4x + 3)(x — 5)

For L.H.S use formula (a + b)(a – b) = a² – b²

⇒ 4x² – 1 = 4x² – 20x + 3x – 15

⇒– 1 = – 17x – 15

⇒ – 1 + 17x + 15 = 0

⇒ 17x + 14 = 0

⇒ 0x² + 17x + 14 = 0

Comparing equation 0x² + 17x + 14 = 0 with ax² + bx + c = 0 we get

a = 0, b = 17 and c = 14

Here a, b, c ∈ R but a = 0

Therefore, the degree of polynomial 0x² + 17x + 14 = 0 becomes 1

Hence (2x + 1)(2x — 1) = (4x + 3)(x — 5) is not a quadratic equation