How to find $x^2 - x$? I'm quite a novice when it comes to maths. I'm on a problem in which I have had to isolate $x$ , through factorials which I completed without problem. However, now I am stuck on a seemingly more minor problem.
The problem I currently have is $x^2 - x = 380$. I know that this can be solved for $x = 20$, however I am unsure how this has been worked out.
I am sorry for this being such a basic question, however I simply have no idea how this was solved.
Thanks,

$$x^2 - x = 380$$
Rewrite this as:
$$x^2-x-380=0$$
Use quadratic formula to solve it now. It is:
$$x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}$$
For:
$$ax^2+bx+c=0$$
Just plug this in:
$$x=\frac{-(-1) \pm \sqrt{(-1)^2-4(1)(-380)}}{2(1)}=\frac{1 \pm \sqrt{1521}}{2}=\frac{1 \pm 39}{2}$$
Which means:
$$\therefore x=20 \text{ or } -19$$
