Thread: how does m = b (or slope=y-intercept

How can I prove that COVAR(x,y)/VAR(x) = b? I'm pretty sure the first part equals m, but I don't see how the slope and y-intercept can be the same thing, unless their both zero.

Any nudge in the right direction would be greatly appreciated.

My understanding is, for

then

So this works if you call the equation , many text books do.

Thanks, pickslides!