How to modify the input function to a system?

Hi

if I have the function x[n] = cos(2*pi*n) in 0=<n<=10 and x[n] = 0 else where

n = -20:1:20;
xn = cos(2*pi*n);
xn(n<0) = 0 ;
xn(n>10) = 0 ;
stem(n,xn)

How will I create the output using the previous input x[n], for example z[n] = 3x[n+3] + 5x^2[5] ?

Answer 1

[Amir Xz]

1. Left Shift:

 xn(end+1:end+3)=xn(1:3); xn(1:3)=[];

2. New signal:

 y = 3*xn + 5*xn(5)^2;