Yarmewh Uaheraity

$12.$ Determine the nes causal system

a$)y(n)=nx(n)$

b$)y(n)={\displaystyle \underset{?}{\overset{?}{}}}k=x(k)$

c$)y(n)=x(n)-x(n-1)$

d$)y(n)=x(n^2)$

e$)$ None af the above

$13.$ The $4-$point Discrete Fourier Transform $($DFT$)$ of a discrete time sequence $(1,0,2,3)$ is

$\backslash$table$[[$a$)2,2+2j,6,2-2j,$b$)6,-1+3j,0,-1-3j$