This is a part of a question on the master/doctor degree graduate school entrance test for Tokyo Univ. in 2016.
The conditions are below
Here is the question.
I have to make a differential equation using y, y', and c.
However, I don't have any ideas to partially derivate F with respect to y'.
I can't ignore y in F(y,y') because it has a relationship with y, can I?
Please tell me how to deal with this problem.