I am only given y= x/3 and am asked to find the general solution. So what I did was get the derivative up until the second order and I multiplied each so that if I were to add them up they would equal zero. The question I have is...how do you choose what to multiply the derivatives by? Because I took a quiz and the first time I did they had x^2y''+7xy'+9y=0 and the second time they had switched it to x^2y''+3xy-3y=0.