Solved
How to input ".." correctly in 1^2+2^2+..+n^2?
When i input "+..+" , it appears two gray block, and i will also display in printed pdf files, it is not beauty.

How to input ".."correctly in 1^2+2^2+..+n^2 or a^2+b^2+..+z^2. etc ( without gray blocks)?


