Need help drawing a line that fits three points on a graph

[giuls21]

I am trying to come up with an inflation rate construction and having trouble coming up with a curve. At the moment I have the following:

X Axis (Dollar Value) Y Axis (Inflation Rate)
$3.10 58%
$.40 22%
$.10 -88%

The X Axis can never be lower than $.10. The y axis can be negative, but there is no y-intercept. Therefore this is akin to a parabola. I am trying to understand how I can craft a curve that runs through these three points and therefore would "fill-in" the rest of the population.

Thank you for the help in advance.

[Kaper]

If just drawning - use trendline, but from the rest of question it seems that you need extra/interpolation.

If you want to fit parabole, you can easily calculate its parameters with the array formula.
Select 3 cells say D7:F7, with the 3 cells selected write the formula and commit it with Ctrl+Shift+Enter)
Assuming your data is in D10:E2 the formula for D7:F7 (again: one array formula for 3 cells commited with CSE, not just Enter):

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See attachment (by the way - read the forum rules and suggestions in chapter: Want to get your question answered quickly?)

[giuls21]

Thank you so much for this response! Do you know how to flatten out the curve so that the highest y axis point is 58%? In other words, 2 on the x axis should equate to some value between 22% and 58% on the y axis, rather than 250%. Thank you again for the help!

[Kaper]

Use other curve type (there is only one parabola equation which goes through 3 points).
Or dont ask that line "runs through these three points"