C h o x 1 ( n ) = x 2 ( n ) = δ ( n + 2 ) + δ ( n − 2 ) . Tính FT của x 3 ( n ) = x 1 ( n ) * x 2 ( n )

$X{}_3\left(e{}^{jw}\right)=e{}^{j4w}+2+e{}^{-jw4}$

$\text{X}{}_3\left(\text{e}{}^{\text{j}\text{w}}\right)=\text{e}{}^{\text{j}4\text{w}}-2+\text{e}{}^{-\text{j}\text{w}4}$

$\text{X}{}_3\left(\text{e}{}^{\text{j}\text{w}}\right)=-\text{e}{}^{\text{j}4\text{w}}-\text{e}{}^{-\text{j}\text{w}4}$

$\text{X}{}_3\left(\text{e}{}^{\text{j}\text{w}}\right)=\text{e}{}^{\text{j}2\text{w}}+\text{e}{}^{-\text{j}\text{w}2}$