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## Main Question or Discussion Point

I've run into these formulas many times but I've never seen how they were derived.

Say you want to fit a line to some data. Your data is a bunch of (xi,yi) pairs.

Through some kind of magic, the slope m and the y-intercept b are given by these formulas:

http://img262.imageshack.us/img262/9250/eb49c97d171bcd52e220911.png [Broken]

http://img407.imageshack.us/img407/5681/bdea06a3287d543f035cac4.png [Broken]

My attempt at deriving them:

I set up a matrix equation Ax=b and use the pseudoinverse to find the least-squares solution: x = inv(A'*A)*A'*b where A' is A transpose.

Annnnnd now I'm stuck. :) How would you go from that to those two formulas? Or maybe I'm headed in the wrong direction...

Say you want to fit a line to some data. Your data is a bunch of (xi,yi) pairs.

Through some kind of magic, the slope m and the y-intercept b are given by these formulas:

http://img262.imageshack.us/img262/9250/eb49c97d171bcd52e220911.png [Broken]

http://img407.imageshack.us/img407/5681/bdea06a3287d543f035cac4.png [Broken]

My attempt at deriving them:

I set up a matrix equation Ax=b and use the pseudoinverse to find the least-squares solution: x = inv(A'*A)*A'*b where A' is A transpose.

Annnnnd now I'm stuck. :) How would you go from that to those two formulas? Or maybe I'm headed in the wrong direction...

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