Q2 of 37 Page 1

Find the value (s) of k, if the quadratic equation 3x2 – k√3x + 4 = 0 has equal roots.

We have quadratic equation,

3x2 - k√3x + 4 = 0


Comparing this equation with standard quadratic equation, ax2 + bx + c = 0


We have a = 3, b = -k√3 and c = 4


We have quadratic formula,



(b2 – 4ac) is called discriminant (or D).


Now, since the roots of this quadratic equation are same,


D = 0


b2 – 4ac = 0 …(i)


Substituting values a = 3, b = -k√3 and c = 4 in equation (i), we get


(-k√3)2 – 4(3)(4) = 0


3k2 – 48 = 0


3k2 = 48


k2 = 16


k = √16


k = 4


Thus, k has two values, i.e., 4 and -4.


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