$ y(t) = K x(t-a) $
if $ x(t)=e^{jwt} $ was inputed to the system
$ y(t) = K e^{jw(t-a)} $
$ = K e^{-jwa}e^{jwt} $
== $ y(t) = K x(t-a) $
$ = K e^{-jwa}e^{jwt} $ ==
