Working with Tenenbaum's ODE page 91, problem 17,

, can't figure it out. Here are some pieces of information that could be useful, given the methods of finding an integrating factor discussed in the chapter:

(a)

(b)

Now I need to take

or it times

or

, and divide it by (a) or (b) so that the result is a function of

, or

. But none of it seems to work. The book says that the integrating factor necessary is

, but I don't see how you could possibly obtain that with the methods discussed in the chapter.