Question

Which of the following is a quadratic equation? 

(a) `x^3-3sqrtx+2=0`                  (b) `x+1/x=x^2` 

(c)` x^2+1/x^2=5`                      (d) `2x^2-5x=(x-1)^2`

Answer 1

(d)`2x^2-5x=(x-1)^2` 

A quadratic equation is the equation with degree 2. 

∵ `2x^2-5x=(x-1)^2` 

⇒ `2x^2-5x=x^2-2x+1` 

⇒ `2x^2-5x-x^2+2x-1=0` 

⇒` x^2-3x-1=0`, which is a quadratic equation