need some help setting up a few problems

Here are the problems I am having difficulty with:

1. Given the characteristic equation of a 4th order differential equation has repeated roots of i and - i,

a) write the general solution of the differential equation

b)write the original differential equation

2.

a) write the general solution near x = 0.

b) find the indicial equation and the exponents at the singularity.

**Those are the 2 problems I am having trouble with. Its all just on how to start.. Here is what im am doing for each of them:**

1.[/B]

A. I dont know how to do....

B.

2. With this you can just substitute

where n = 0 to infinity and its appropriate derivatives. correct?