Question

If the following quadratic equation has two equal and real roots then find the value of k :
$x^2+2kx+4=0$

Answer 1

$x^2+2kx+4=0$

For two equal roots, $D=0$

$D\equiv b^2-4ac$

$0=4k^2-4\left(4\right)\left(1\right)$

$\Rightarrow 4k^2=4^2$

$\Rightarrow k^2=4$

$\Rightarrow k^2-4=0$

$\Rightarrow k=\pm 2$

$\Rightarrow k=2,-2$