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

Find the roots of the following quadratic equation by the method of completing the square: $x^{2}-8x+12=0$

Examine whether the following equation is quadratic or not: $(3x - 4)^2 - (2x - 3)^2 = 7$.

Check whether the following is a quadratic equation:
$x(2x + 3) = x^2 + 1$

In a right triangle,the length of the hypotenuse is $2\,cm$ more than the length of the base and $1\,cm$ more than twice the length of the altitude. Find the length of the hypotenuse. (in $,cm$)

The roots of the quadratic equation $\ldots \ldots \ldots \ldots$ are $-4$ and $5$.