Where do the squared values in statistical calculations come from?

[smaan]

Homework Statement

I have no idea where the sum of x^2 comes from, from the information I posted. I know it must be something pretty simple but its completely going over my head. In the picture that I've attached, I am wondering where the 2431.72, 4901.66, and 3252.44 come from. Thank you for any help.

Homework Equations

The Attempt at a Solution

 

[SteamKing]

What did you try to get Sum(x)? Sum(x^2)?

 

[smaan]

What did you try to get Sum(x)? Sum(x^2)?

I tried squaring x, but obviously that is not correct.

 

[SteamKing]

Did you try, you know, adding up the columns of figures? That's what Sum(x) means. The other one is trickier: you've got to square each number, and then add them up.