I used Newton's method several times earlier (40 years ago). Actually it was a Fortran program from IMSL (and also from NAG) that used a combination of bisection and Newtons's method, to make sure that a solution should be found. They worked Very well. There are however problems that are more difficult to solve. E.g. how to find the biggest solution OR how to find all solutions. Consider (x-3)*(x-2)*(x-1). Obviously the zeroes are 1, 2 and 3. But (x*x+1)*(x-3) only has one zero. / Br Anders