Solve the ordinary differential equation

x^{2}y'' - 3xy' + 3y = x^{3}cosx

I am working on this question for 2 days and I coudn't get to the final result.

we have to use the power series to solve this question. so I substitute y= sum(n=0 to infi)Ckx^{k}, and also for y' and y'' into the equation. also for the RHS too.

please help me to solve it.