Có hai tín hiệu x ( n ) = δ ( n + 2 ) + δ ( n − 2 ) . Tính FT[x(n)].

$X\left(e{}^{j\omega }\right)=-2\text{c}\text{o}\text{s}2\omega$

$X\left(e{}^{j\omega }\right)=2\text{c}\text{o}\text{s}\omega$

$X\left(e{}^{j\omega }\right)=2\text{c}\text{o}\text{s}\omega$

$X\left(e{}^{j\omega }\right)=2\text{c}\text{o}\text{s}2\omega$