If one of the roots of the quadratic equation $x^{2}-ax-8=0$ is $-4$,then $a = \ldots \ldots \ldots \ldots$.

If one of the roots of the quadratic equation $x^{2}+6x+k=0$ is $-4$,then $k = \ldots$.

Examine whether the following equation is quadratic or not: $\frac{x-2}{x+2} - \frac{x+2}{x-2} = \frac{3}{7}$

Verify whether the given value of $x$ is a solution of the quadratic equation or not: $4 \sqrt{3} x^{2} + 5 x - 2 \sqrt{3} = 0$; $x = \frac{\sqrt{3}}{4}$.

If one of the roots of $x^{2}-2x-c=0$ is $5$,the other root is ...........

The value of the discriminant $D$ of the quadratic equation $x^{2} + 5x + 1 = 0$ is $\ldots \ldots \ldots \ldots .$