This is what you should be doing :
\(|x^2-20x-1|=20\\~\\ \color{blue}x^2-20x-1=20 \qquad or \qquad x^2-20x-1=-20 \\\)
Think about this simple example
|x|=5
What this says it that the distance x is from 0 is 5. So x could be 5 or maybe -5.
If you let \(y=x^2-20x-1\)
then your question is asking, for what values of x is y 20 units away from 0.
So y can equal 20 or y can equal -20.
You will get 4 answers. They will not necessarily all be real.
I expect you are only interested in real answers so if some are not real you can discard them.
Now you must substitute the real ones into the original equation to check that they work properly.
Discard any that do not work.
Is that enough help ?