Question

Find the value of k for which the quadratic equation 9x² − 3kx + k = 0 has equal roots. 

Answer 1

It is given that the quadratic equation 9x² − 3kx + k = 0 has equal roots.  

∴ D = 0 

⇒ (−3k)² − 4 × 9 × k = 0 

⇒ 9k² − 36k = 0

⇒ 9k(k − 4) = 0

⇒ k = 0 or k − 4 = 0 

⇒ k = 0 or k = 4 

Hence, 0 and 4 are the required values of k.