Question

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

• A. 0
• B. 2 , 0
• C. -2, 0
• D. $\pm 2$

Answer 1

The correct option is D

$\pm 2$

Given, the roots of quadratic equation $9x^2+6kx+4=0$ are real and equal.

$\text{Discriminant,}\Delta =b^2-4ac\Delta =36k^2–4\left(4\right)\left(9\right)=36k^2–4\left(36\right)$

The roots of quadratic equation are real and equal then $\Delta =036k^2–4\left(36\right)=0k^2-4=0k^2=4k=\sqrt{4}\therefore k=\pm 2$