Does VB6 have a function to solve Determinants?

I also need to curve fit a low order polynomial y = a +bx +cx^2 +dx^3 through 4 (x,y) points. I appreciate (and understand) the Gauss Elimination method.

My question is, "is there a function in Visual Basic 6 that I can use which finds the coefficients for me"?. I guess I'm thinking back many years to school where I think I remember "determinants" or something like that.

Well, the Gaussian Elimination method will solve your system directly, so I'm a little unsure why you're asking how to find those coefficients. I'd be surprised if you couldn't find a version of it someone wrote, though it's not that hard to write either.

Another method for solving your equation is using Cramer's rule and determinants. With only a 4x4 matrix, you could probably find an explicit formula for the determinant online without much trouble. If not, I'll derive it for you. There's no built in determinant function for VB, though I'm sure it exists in some library somewhere.