Chart: trendline between points?

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Hello.
Please, I have some lines in my chart with visible pointers...

How can I make something like this idea?
http://www.physics.purdue.edu/resources/excel_straight_line/

I need a linear aproximation like that, a trendline.


Google'd told me that link, but nothing about Fast-Reports.

I'll appreciate any help.
Thanks in advance!