Sorry im having abrain f**t.
Edit: apparently the word "f_a_r_t" isn't allowed.
\(-5-2\sqrt2\) is an irrational number and is already in its most simple form
Since you found out that the word you wanted to use was not allowed why didn't you just use a different, more appropriate one.
Certain words offend some people and that is why they are censored out.
The approx value is -7.82 as iiavx has already told you.