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# Econometrics Question - Proof watch

1. Hello everyone!

I just started taking econometrics and I'm having trouble with this proof.

I know that sum(xi-xbar)(yi-ybar) = sum(xi-xbar)yi but I can't figure out how to translate that into this proof. Any help would be appreciated! Thank you.
2. Expand the brackets to obtain

Now use the fact that and to prove the result.
Note: and can be taken out of the summations as they are numerical values.
3. (Original post by Cryptokyo)
Expand the brackets to obtain

Now use the fact that and to prove the result.
Note: and can be taken out of the summations as they are numerical values.
It seems I was going about the question the wrong way. Thank you so much for your help! I believe I solved it.

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Updated: February 4, 2017
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