Least Squares Parabola

**matlabber** · 06-09-2012 01:45 PM

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**Dragan** · 06-09-2012 05:05 PM

Originally Posted by matlabber

Hi all

I have been trying to find the values of the coefficients for the least squares parabola:

y = a + bx + cx^2

I have taken partial derivatives wrt a, b, c and now have three equations, but I don't know what to do next...any suggestions? Have you solved this before?

thank you very much!!

I can help with LaTeX in exchange for help thank you very much

Your system of normal equations should look like the following:

$\Sigma y=an+b\Sigma x+c\Sigma x^{2}$

$\Sigma xy=a\Sigma x+b\Sigma x^{2}+c\Sigma x^{3}$

$\Sigma x^{2}y=a\Sigma x^{2}+b\Sigma x^{3}+c\Sigma x^{4}$

**Dason** · 06-10-2012 04:19 PM

It's a system of three equations with three unknowns (a, b, c). Everything else is taken as a known fixed value. If I told you to solve for a, b, c given the following equations could you do it?

1 = 3a + 4b - 2c
2 = 7a - 13b + 8c
92 = a + b - c

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