How to prevent Solve from DSolve?

*Subject*: [mg888] How to prevent Solve from DSolve?*From*: chen at fractal.eng.yale.edu (Richard Q. Chen)*Date*: Fri, 28 Apr 1995 00:45:48 -0400*Apparently-to*: mathgroup-send at christensen.cybernetics.net*Organization*: Yale University

Hi, I find it very frustrating that Mma always tries to give explicit solutions to an ODE, even if the solutions are so complicated as to be useless. For example In[2]:= Needs["Calculus`DSolve`"] In[3]:= DSolve[2 y[x] + (x + y[x]) y'[x] == 0, y[x], x] Out[3]= {{y[x] -> 1/3 2 > -2 x + (3 2 x ) / 3 6 3 2 1/3 > (54 x + 27 C[1] + Sqrt[-2916 x + (54 x + 27 C[1]) ]) + 3 6 3 2 1/3 1/3 > (54 x + 27 C[1] + Sqrt[-2916 x + (54 x + 27 C[1]) ]) / (3 2 )} > , {y[x] -> 2 > -2 x - (3 (1 + I Sqrt[3]) x ) / 2/3 3 6 3 2 1/3 > (2 (54 x + 27 C[1] + Sqrt[-2916 x + (54 x + 27 C[1]) ]) ) - 3 > ((1 - I Sqrt[3]) (54 x + 27 C[1] + 6 3 2 1/3 1/3 > Sqrt[-2916 x + (54 x + 27 C[1]) ]) ) / (6 2 )}, 2 > {y[x] -> -2 x - (3 (1 - I Sqrt[3]) x ) / 2/3 3 6 3 2 1/3 > (2 (54 x + 27 C[1] + Sqrt[-2916 x + (54 x + 27 C[1]) ]) ) - 3 > ((1 + I Sqrt[3]) (54 x + 27 C[1] + 6 3 2 1/3 1/3 > Sqrt[-2916 x + (54 x + 27 C[1]) ]) ) / (6 2 )}} I would like to have Mma out put something like f(x,y) == C[1] so that I will know what kind of simpler function f(x,y) may be. I can then choose to solve for y in terms of x if it is desirable. In this particular case I had to use pencil and paper and I obtained the much simpler implicit solution f(x,y) = y*(y+2x)^2 = C[1] This is the kind of solution I wanted. How can I prevent DSolve from using Solve to give complicated solution? Thanks for any info. -- Richard Q. Chen chen at fractal.eng.yale.edu