Question

Which of the following is a quadratic equation ?

A) x³ – 6x² + 2x -1 = 0 

B) x² + 1/x² = 2 

C) x + 1/x = 3 

D) (x + 1) (x + 2) (x + 3) = 0

Answer 1

Correct option is (C) x + 1/x = 3

(A) \(x^3-6x^2+2x-1=0\) is a cubic equation.

(B) \(x^2+\frac{1}{x^2}=2\)

\(\Rightarrow x^4-2x^2+1=0\) is a quartic equation.

(C) \(x+\frac{1}{x}=3\)

\(\Rightarrow x^2-3x+1=0\) is a quadratic equation.

(D) \((x + 1) (x + 2) (x + 3) = 0\)

\(\Rightarrow(x^2+3x+1)(x+3)=0\)

\(\Rightarrow x^3+6x^2+10x+3=0\) is a cubic equation.

Answer 2

Correct option is C) x + 1/x = 3