I'm faced with a problem where I need to determine the intersecting point of three different surfaces. Normally I would do this by using the incredibly painful method of Lagrange multipliers. However, this computation needs to be done relatively quickly and I can afford some error, in the range of about +/- 3%. I really don't want the computation requirement of the LM method and would prefer something more simple, does anyone know of something else? Preferably something that can be easily coded into matlab? I was told about a method thats used for CAD systems, surface-surface-intersection which apparently is a numerical search method for defining this point. However, I just can't seem to find any info on it. The surfaces I am working with are define by second order multi variable polynomials of the form: x2+ x + xy + y + y2+C. Can anyone help me out?