Who gave the general formula to solve quadratic equations?

Find the roots of the following quadratic equation by using the quadratic formula,if they exist: $(x+4)(x+5)=3(x+1)(x+2)+2x$

If $x=2$ is one of the solutions of the quadratic equation $k x^{2}+3 x-4=0,$ then what is the value of $k$?

Find the roots of the following quadratic equation using the quadratic formula,if they exist: $\frac{1}{x+1} + \frac{2}{x+2} = \frac{4}{x+4}$; $(x \neq -1, -2, -4)$

Find the roots of the following quadratic equation by the method of completing the square: $x^{2}-4x-8=0$

What is the value of $k$ if one of the roots of the quadratic equation $x^{2} + 6x + k = 0$ is $-4$?