How we can enter the following operators in MATLAB ?

1- x(n)=δ(n)

2- δ(n-4)

3- 2^n u(n-3)

Answer 1

[Walter Roberson]

For delta, see:

https://www.mathworks.com/help/symbolic/dirac.html

https://www.mathworks.com/help/symbolic/kroneckerdelta.html

For u:

https://www.mathworks.com/help/symbolic/heaviside.html

However, when people write in terms of u, they often mean the unit step function. To achieve the unit step function you need to use sympref to set the value of HeavisideAtOrigin according to your needs.