Quadratic polynomial can be factored using the transformation $ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right)$, where $x_{1}$ and $x_{2}$ are the solutions of the quadratic equation $ax^{2}+bx+c=0$.
$$-n^{2}+4n=0$$
All equations of the form $ax^{2}+bx+c=0$ can be solved using the quadratic formula: $\frac{-b±\sqrt{b^{2}-4ac}}{2a}$. The quadratic formula gives two solutions, one when $±$ is addition and one when it is subtraction.
$$n=\frac{-4±\sqrt{4^{2}}}{2\left(-1\right)}$$
Take the square root of $4^{2}$.
$$n=\frac{-4±4}{2\left(-1\right)}$$
Multiply $2$ times $-1$.
$$n=\frac{-4±4}{-2}$$
Now solve the equation $n=\frac{-4±4}{-2}$ when $±$ is plus. Add $-4$ to $4$.
$$n=\frac{0}{-2}$$
Divide $0$ by $-2$.
$$n=0$$
Now solve the equation $n=\frac{-4±4}{-2}$ when $±$ is minus. Subtract $4$ from $-4$.
$$n=-\frac{8}{-2}$$
Divide $-8$ by $-2$.
$$n=4$$
Factor the original expression using $ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right)$. Substitute $0$ for $x_{1}$ and $4$ for $x_{2}$.
