What is "Variation of Parameters"? 1. The problem statement, all variables and given/known data None. General. 2. Relevant equations I don't know. :( ? 3. The attempt at a solution ? I am taking a class right now on engineering analysis (which I am finding it to be more like partial differential equations mixed with boundary value problems on steroids) and the way that my professor is explaining stuff to us doesn't make a lot of sense to me and I've tried asking him and it doesn't really seem to be helping. I've also tried looking it up on the internet as well, and they all pretty much say the same thing, which doesn't really help me understand it either. So...what IS "variation of parameter"? Are they really good examples that show how it is used and how to solve problems with it? We don't have TA's or anything like that at my school, and because it's considered to be a graduate level class, we also don't have any tutors for it either. :( We were told that we had to use this method in the one of the programs that was posted on here: https://www.physicsforums.com/showthread.php?t=265432&highlight=cauchy-euler And I didn't understand what it meant by "using variation of parameters' method. So any help that can explain what my prof is talking about would be GREATLY appreciated!