# Math Help - Have I done this manipulation correctly?

1. ## Have I done this manipulation correctly?

I started with this

and rewrote it as this, factoring out sum(ei)

Is this correct? What I am unsure about is the bottom of the fraction, should it be sum(xj-xbar) or sum(xi-xbar)?

It's a question in which the final answer has (xj-xbar) on the bottom of that fraction (once you use common denominator) I am trying to establish if it is a typo.

2. ## Re: Have I done this manipulation correctly?

No, that is not correct. The $x_i$ terms depend upon i and are also in the sums.

3. ## Re: Have I done this manipulation correctly?

Oh, so I cant even do that manipulation...