clear all; clc;

freqz([0.75 1.25 1 1 1.25 0.75],[1 0 0 0 0 0]);
n=0:199;

x=sin(pi.*n./2)+5.*cos(pi.*n);
y=filter([0.75 1.25 1 1 1.25 0.75],[1 0 0 0 0 0],x);

figure
stem(n,x)
hold on
stem(n,y);
hold off
xlabel('n');
legend('x[n]','y[n]');