Ok here's my problem, i'm really having trouble with:

"If the equation P(x)y" + Q(x)y' + R(x)y = 0 is not exact, it can be made exact by multiplying by a suitable integrating factor µ(x). Thus, µ(x) must satisfy the condition that the equation µ(x)P(x)y" +µ(x)Q(x)y' + µ(x)R(x)y = 0 is expressible in the form [µ(x)P(x)y']' + [S(x)y]' = 0 for some function S(x)."

So, what i need to do then is show that µ(x) must be a solution of the adjoint equation P(x)µ'' + [2P'(x) - Q(x)]µ' +[P"(x) - Q'(x) + R(x)]µ = 0

Thanks for any and all help!