For what value of k the quadratic equation 9x2+8kx+16=0 has equal roots?

Question

For what value of k, the quadratic equation 9x²+8kx+16=0 has equal roots?

Answer 1

Given equation, 9x²+8kx+16=0

Here, a = 9, b = 8k, c = 16

Now, b² - 4ac = 0

(8k)² - 4 .9 .16=0

64k² - 576=0

64k² = 576

k² = 576/64

k² = 9

k² = 3²

k= ± 3

The value of k so that the equation 9x²+8kx+16=0 has equal roots is 3 or -3.