Need some help with data management

Maksimus

Hi all,

First of all I have gathered some data from my experiments witch looks something like this:
[img=http://img689.imageshack.us/img689/9518/79173624.png]
Now I do a linearization for my data using Matlab command:
y=feval(fit(a(l:o,1,1),a(l:o,2,1),'poly1'),a(l:o,1,1));
Results looks like this:
[img=http://img199.imageshack.us/img199/6116/59180265.bmp]
Now I do a interpolation using for example 5th order poly and get this:
[img=http://img844.imageshack.us/img844/8876/60889328.png]
I calculate the peak value and calculate -3dB value of peak value and get a line as you can see in the image:
[img=http://img213.imageshack.us/img213/9484/42165661.png]

Now my question is, what is the fastest and the best function to find the intersection x values of the 5th order polynomial and the line?

Thank you for your answers in advance,
Regards,
David.