I am trying to solve the following differential equation: `DSolve[{y''[x] == A*B (y[x])^2, y'[0] == -B*C, y'[-D] == 0}, y[x], x]` For my system, this differential equation would be valid in the range of -D < x < 0. Mathematica says: "For some branches of the general solution, unable to solve the conditions." Without boundary conditions, I get a solution consisting of a Weierstrass elliptic function, but Mathematica is not able to solve for the boundary conditions, even if I use a simpler series expansion of the solution. In general, I am not directly interested in y[x], but in y[0]/C. I have experimental data for sets of y[0], B, C and D. Ideally, I would like to have a general solution for y[0]/C to be able to analyze it and to compare the behavior with my experimental data, but I am not able to solve the boundary value problem. Maybe a part of the problem is that the Weierstrass elliptic functions are periodic and I only need one branch of that ? If a general solution is not possible, a numerical solution could also be helpful. How could I calculate the value of A for the data sets of y[0], B, C and D ? I appreciate any help.