Equations in regards to regression analysis

Melina

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Joined
May 18, 2012
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1
Hi!
Ive been given two questions I really dont understand. The first one is:

Prove that: Sum of (Xi - x-bar)(Y1- Y-bar) = Sum of X1 (Y1 - Y-bar)

The other one is

Prove that:

Sum of (X1 - x-bar)2 = Sum of X1(X1 - x-bar)

With the second one i wondered if it based on the X-bar being (Sum of X)/n so rewriting it means:

X(X- Sum of X/n) ---> X2 - (Sum of X)2 /n

But it dosent seem correct when I apply it to real numbers. Please help me with this!

Thank you!
 
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