I fit a trendline to some data I have, shown below.
809920.89 1688.50
811026.35 1685.90
812370.50 1680.80
813553.47 1673.80
814357.32 1670.65

the equation given by excel (polynomial 2nd degree fit) is
y=-4e-7x^2+.6676x-267718

however, if you plug the first x point (809920) into this equation, the
value given is over 10,000.

where is the problem?
the trendline appears to fit, but the equation given doesn't fit at all