A linear operator must meet the following conditions:
\[ S\{\alpha x[n]\} = \alpha S\{x[n]\} \]
\[ S\{x[n] + y[n] \} = S\{x[n] \} + S\{y[n] \} \]
A linear operator must meet the following conditions:
\[ S\{\alpha x[n]\} = \alpha S\{x[n]\} \]
\[ S\{x[n] + y[n] \} = S\{x[n] \} + S\{y[n] \} \]