Regarding the titles on questions,
Is better
The author of the book, the chapter number and the exercise number.
The exercise as explicit or informative as possible (not always possible tho :( ).
Both 1. and 2. (whenever possible).
?
One cons that I find with 1. is that if you don't have the book, then the title will be misleading and probably a waste of time when clicking. And a pro, if you have the book, then the search would be really easy (more easy than 2.) one just need to type for the author of the book, chapter, exercise, and done i.e. no need to type MathJax and check for the all the suggestions (which sometimes none of them have what one is looking for exactly).
See for example, for 1.
https://math.stackexchange.com/search?q=rudin+exercise+chapter+is%3Aq
Edit
This question first had
- Courant John 4.6 16
then
- Courant John 4.6 Problem 16 - Prove that $\int\int_R e^{-(x^2+y^2)}dx dy=ae^{-a^2}\int_0^{\infty}\dfrac{e^{-u^2}}{a^2+u^2}du$
and then
- Prove that $\iint_R e^{-(x^2+y^2)}\,dx\, dy=ae^{-a^2}\int_0^{\infty}\frac{e^{-u^2}}{a^2+u^2}\,du$