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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`
Solution
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.
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