a question about Exel

hello .
I give X and Y values and get the chart but I also want to have the chart equation (formula --> like Y=aX+b).
is it possible ?

I have win Xp exel .
thanks

right click on the line on the chart and select "add trendline". Under the options there is a checkbox "display equation on chart" that should be checked.

If you are writing a program, you can get clue when you create a Macro, then see its code.

:)
thanks alot .