Cho dãy x ( n ) N = x 1 ( n ) N (   * ) N x 2 ( n ) N = ∑ m = 0 N − 1 Unsupported  x 1 ( m ) N x 2 (

$\text{X}(\text{k}){}_{\text{N}}=\text{X}{}_1(\text{k}){}_{\text{N}}(\text{*}){}_{\text{N}}\text{X}{}_2(\text{k}){}_{\text{N}}$ $$

$X(k){}_{\text{N}}=X{}_1(k){}_{\text{N}}\cdot X{}_2(k){}_{\text{N}}$

$X(k){}_{\text{N}}=X{}_1(k){}_{\text{N}\cdot }X{}_2(-k){}_{\text{N}}-$

$X(k){}_{\text{N}}=X{}_1(k){}_{\text{N}}\left( {}^{\text{*}}\right){}_{\text{N}}X{}_2(-k){}_{\text{N}}$ $$