find the gradient of a line on a chart

[Santiago Zawojski]

I have the following data:

3
6
11
18
27
38
51
66
83
102
123
146
171
198
227
258
291
326
363
402

Which is plotted on a chart.

How do I find the gradient of that line?

Thanks very much for any help.

 

[Leo Heuser]

The points specify a parabola and not a line,
so it's not possible to find the gradient, unless
you specify, at which point you want it.

If you create a polynomic tendency line to the
curve (I have the X-values going from 0 to 19)
and checkmark "Display equation in chart" (or similar)
the formula is

Y = X^2 + 2X +3

You can the differentiate to get the equation for
the gradient of the tangents to the curve, that is

Y' = 2*X + 2

so e.g. the tangent to the point (3,18) has the
gradient

Y' = 2*3 + 2 = 8

--
Best Regards
Leo Heuser
MVP Excel

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