Implementing a constant_coeffecient linear difference equation in Matlab

hi, please if anyone can help, i will realy be gratefull, its important to get this code or atleast any part of it, or where to start with it , and without using the DSP tool box.......



write a program to implement the constant_coeffecient linear diffrence equation:

y=Σbi x(n-i) +Σai y(n-i), where for x : (0<=i<=N-1), and for y: (1<=i<=M-1)

for general values of N and M. Assume zero initial conditons, i.e:y=0, for n<0.
1. use the program to determine, and plot the impulse response of the following system:
a-y=x+.9y(n-1)-(.9)^10x(n-10)
is theis system recursive or non recursive, and is it IIR, or FIR?

b.y=.9y(n-1)+x

2. use the prog. to compute and plot y for the examples belowrun the prog. for 30 samples)

a. x=.8^n u, and h=1, 0<=n<=4.

b. x=.5^n u, and h= (.9^n)u,

c. x=cos(2Πn/8 ), and h=1, 0<=n<=7..

Re: matlab needed help

use "symsum" for calculating series.
use impulse to find impulse response!