I have a question about the Variation of Parameters method... I have no idea whether this is an easy or difficult question to answer.
With the Variation of Parameters method, we start with this concept:
Here, an assumption is made that:
My question is why? I understand that it all works out, but I'd like to understand what the reason is that we can do this. Every source of information I've come across states this assumption, but not a single one I've found ever explains the reasoning for it.
Can anyone enlighten me?