How to find Y for known X on a 6th order polynomial trendline equation?

[DominicWright01]

I have a set of data on an excel sheet and the only trendline which matches the data close enough is a 6th order polynomial. I want to extract the X value for a known Y value however I cannot simply rearrange the equation (bearing in mind I have to do this over 100 times).

It is not as simple as changing the x-axis and y-axis around due to my data, you can see the image below for reference.

Is there a way I can change the subject to provide me with an equation which show X=....?

Thanks

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[PaddyD]

Hi - welcome to the board.

A good place to start would be:

Trendline coefficients


I suspect that a 6th order solution is going to be horribly over-fitted.

Formulas of the form described here:

Excel Tips From John Walkenbach: Chart Trendline Formulas


..can be used to extract the coefficients.