Question

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

• A. -1 or 1
• B. 1 or 3
• C. 2 or 3
• D. -2 or 2

Answer 1

The correct option is D -2 or 2

Given, the roots of quadratic equation $9x^2+6kx+4=0$ are real and equal.
Then,
$\text{Discriminant,}D=0\Rightarrow b^2-4ac=0\Rightarrow 36k^2–4\left(9\right)\left(4\right)=0\Rightarrow 36k^2–4\left(36\right)=0\Rightarrow k^2-4=0\Rightarrow k^2=4\Rightarrow k=\sqrt{4}\therefore k=\pm 2$