Question

Relatively quick question concerning ordinary least squares explanation from wikipedia. Explanation below:

Answer 1

In the attached jpeg, for part to the right of the second equal sign, I am confused either by the sigma summation notation, or about what the correct answer is. When they write\[1/n\], do they mean sum i = 1 to n, or do they mean to divide the entire sum by n? ... okay, I think I just figured out my answer, they are dividing by n... I'm going to close this, so as not to crowd the open question space.