This is really strange: If i rewrite a potens function i get a function which should not be possible (it does not give the same values). What did i do wrong? Y = b*X^a lnY = ln(b*X^a) lny = lnb + ln X^a lnY = lnb + a*lnx we raise both sides to e Y = b+ e^(a*lnx)=b+( e^lnx)^a = b + X^a I think b+ x^a is very diffrent that b*x^a ????