Question

If the equation $9x^2+6kx+4=0$ has real and equal roots, then find the value of k.

• A. zero
• B. either 2 or zero
• C. either –2 or zero
• D. either 2 or –2

Answer 1

The correct option is D

either 2 or –2

$9x^2+6kx+4=0$,

Value of discriminant D = $36k^2–4\left(4\right)\left(9\right)=36k^2–4\left(36\right)$

The roots of quadratic equation are real and equal when D=0

$36k^2–4\left(36\right)=0$

$k^2=4$

k = -2 or 2