# Error in center-focus length of an ellipse

I have an equation of ellipse in the form: $$Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0.$$

I would to calculate the semi-axis major and minor and the center coordinates of the ellipse.

I plugged everything in formulae in a simple JS program. Everthing is right but the semi-minor axis length is wrong (I used Geogebra to compare the result), and as the answers of Osmund Francis tell, semi-minor axis length depends on s the distance center-focus and other things. It seems that there is a problem in $s$.