Non-homogeneous differential equation

(x2 + 1)y'' + 3xy' - 4y = cosh(x)

A. Find two linearly independent power series solutions to the homogeneous equation

(x2 + 1)y'' + 3xy' - 4y = 0

B. Find a particular solution to the original differential equation by using the MacLaurin series for f(x) = cosh(x), and give the general solution y = yh + yp

NOTE: Use the recurrence relation to find the first 4 non-zero terms of the series.

I am just confused at where to start. Please tell me how I should start or give hints. After I've read all the advice I'll come back with my solution and look for more help because this section confuses the heck out of me.

Thanks.