Question

If the equation $9x^2+6kx+4=0$ has 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

Step 1:- For, $9x^2+6kx+4=0$, value of discriminant $D=36k^2–4\left(4\right)\left(9\right)=36k^2–4\left(36\right)$

Step 2:- The roots of quadratic equation are real and equal when $D=0$

Step 3:- $36k^2–4\left(36\right)=0⟹k^2=4$

$k=-2or2$