Hi again, For clarity, here's the maxima input for the equation: f1: 0 = (((u - t)^(x - 1) * x) / (a * exp(b * u) + u)) - ((u - t)^x * (a * b * exp(b * u) + 1)) / (a * exp(b * u) + u)^2 Sorry for the confusion in my previous post with the output only. Thanks. Cheers, -- Seb