For what value of k the quadratic equation 9x2+6kx+4=0 has equal roots

Question

Find the value of K for which the quadratic equation 9x²+6kx+4=0 has equal roots.

Answer 1

Given equation, 9x²+6kx+4=0

Now, b² - 4ac = 0

(6k)²- - 4 .9 .4=0

36k² - 144=0

36k²=144

k²=144/36

k²= 4

k²= 2²

k= ± 2

The value of k so that the equation 9x²+6kx+4=0 has equal roots is 2 or -2.