Recently I've stumbled upon the same question as here: What happens to the position function when an oscillator is overdamped and does not have angular frequency?
And the answer that I preferred (the one by CuriousKev) was perfect until the last sentence, "Since we can add solutions to get a new solution, the most general is:
X = A−r1t + B-r2t "
I've tried searching for the "adding two solutions to get final solution" theory but I either get mistaken for chemistry questions or other unrelated mathematical questions, so could someone link me to the right place or explain this usage of solution(s) addition?
I could be posting the question in the wrong place (as in maybe I should ask such question on maths.stackexchange instead?) It is my first question around this website; so apologies in advance.