Hi all'

I am studying a paper about metal forming and I have a problem about data fitting. this problem has 18 pair of inputs (x,y) that are obtained from experiment and has 9 constants. I want to obtain this constants. I attached file.I am trying to solve that by using of Maple v.13. In fact at the mentioned paper , authors have obtained these constants and I don't understand how. I'm waiting your help.

thank u