Question

From the following equations, which one is the quadratic equation?

Options

• `5/x - 3 = x^2`

• x(x + 5) = 4

• n – 1 = 2n

• `1/x^2(x + 2) = x`

Answer 1

x(x + 5) = 4

Explanation:

Option: [A]

`5/x - 3 = x^2`

`(5 - 3x)/x = x^2`

5 – 3x = x³

x³ + 3x – 5 = 0

⇒ This is not a quadratic equation.

Option: [B]

x(x + 5) = 4

x² + 5x = 4

x² + 5x − 4 = 0

⇒ This is a quadratic equation.

Option: [C]

n − 1 = 2n 

This is not a quadratic equation.

Option: [D]

`1/x^2 (x + 2) = x`

x + 2 = x³

x³ – (x + 2) = 0

x³ – x – 2 = 0

⇒ This is not a quadratic equation.