It appears that Mathematica is not evaluating roots of any form at all. N[ ] does not work. It just leaves numbers such as sqrt 2 + sqrt 3. It does not even bother to evaluate something like sqrt 4. Is there a setting that I have changed that causes this, or do I need to reinstall it?
You can try control-=, then "sqrt 2 + sqrt 3", if you don't know the proper syntax, and Mathematica will try to guess what you mean. It will show its guess as a properly formed expression, which you can accept and evaluate.
Mathematica requires correct syntax, and is case sensitive. It also distinguishes between exact and approximate numbers.
In:= (* it returns the same to represent an exact number *)
In:= (* we can ask for an approximate representation *)
In:= (* or if we give it an approximate number, we get one back *)
In:= N[Sqrt, 100]