+324 I know I sound a little stupid by saying this, but in one of my textbooks, I saw this sign and I got all confused. What does it mean and how is it any different from the second one?
Image 1: 
Image 2: 
+118677 I just wrote a post explaining it and now it has disappeared. 
But what you have said is correct.
+118677 The first one says square all the terms, then add them up.
the second one is the other way around.
Add up all the terms and square the answer.
for example
\(\displaystyle{\sum_i^3}x_i^2=1^2+2^2+3^2=1+4+9=14\\~\\ \left(\displaystyle{\sum_i^3}x_i \right)^2=(1+2+3)^2=6^2=36\)
