Can anyone give me a hand here. I have been trying to solve this problem for weeks, but lead me no where. I want to find the roots of the following function
$f(d_1, d_2)=$$\sum_{i=0}^n{[P(e_i)-P_i^L]^2+[P(e_i)-P_i^u]^2}$$
Where:
$P(e_i)=\frac{1-e^-(\frac{a_i}{d_2})^d_1}{1-e^-(\frac{b}{d_2})^d_1}$
I can take the derivative of the function with respect to both d1 and d2 without any problem, but I don't know which kind of numerical method to apply. Can anyone point me in the right direction, please