I'm using Excel 2003. Excel is giving me the wrong equation for the
trendline it produced. The curve resembles a parabola pointed downward with
a positive offset on the y-axis. The x-axis has points -80, -70, -60, ...,
60, 70, 80. I changed the y-axis so that it crosses the x-axis at point
zero. I do not believe that zero on my x-axis is zero according to the way
it comes up with the trendline equation. I wish to figure out how to set up
my x-axis with positive and negative numbers and still have the equation for
the trendline be accurate.