1. The problem statement, all variables and given/known data Solve: y'''=(y'')2 2. Relevant equations 3. The attempt at a solution Basically easy, use the substitution y'' = p and solve through the equations. I end up having this: y=-(x+c1)ln|x+c1| + c2x + c3, which is what I listed in the answers as well. My question is about p≠0 which I get while solving the first integral. p=y''=0 is a solution to the equation. y''=0 means y'=c means y=cx+c Is this included in the solution? I don't think so, and then it should be listed as a solution as well, but it's not. Am I missing something, or it's already in the first solution?