For what value of k the quadratic equation 9x2+kx+1=0 has equal roots

Question

Find the value of k for which the quadratic equation 9x²+kx+1=0 has equal roots

Answer 1

Given equation, 9x²+kx+1=0

Now, b² - 4ac = 0

(k)² - 4 .9 .1=0

k² - 36=0

k² = 36

k² = 6²

k = ± 6

The value of k so that the equation 9x²+kx+1=0 has equal roots is 6 or -6.