Question

Find the nonzero value of k for which the roots of the quadratic equation $9x^2-3kx+k=0$ are real and equal.

Answer 1

For real and equal roots, $b^2-4ac=0$

$\Rightarrow (-3k{)}^2-4\times 9\times k=0$

$\Rightarrow 9k^2-36k=0$

$\Rightarrow 9k(k-4)=0$

$\therefore k=4ork=0$