I'm trying to do some symbolic calculation like this:
Substitute (11.2) into the last two of equations (11.1) and, in turn, substitute these into the first of equations(11.1),
I want to obtain a fourth-order differential equation that is
I have read some material in official documentation, but i still don't know how to do this in Mathematica. Can somebody help me about this, or just tell me to which book/website I should refer so that I can do the calculation in Mathematica.