Write the value of k for which the quadratic equation

The given quadric equation is $x^{2}-k x+4=0$, and roots are equal.

Then find the value of k.

Here, $a=1, b=-k$ and, $c=4$

As we know that $D=b^{2}-4 a c$

Putting the value of $a=1, b=-k$ and, $c=4$

$=(-k)^{2}-4 \times 1 \times 4$

$=k^{2}-16$

The given equation will have equal roots, if $D=0$

$k^{2}-16=0$

$k^{2}=16$

$k=\sqrt{16}$

$=\pm 4$

Therefore, the value of $k=\pm 4$