Cho X ( k ) N = e − j 2 π 4 k + 3 4 e − j 2 π 4 k 2 + 1 2 e − j 2 π 4 k 3 + 1 4 e &#x221

$\text{x}(\text{n}){}_4=\left\{\frac{3}{\underset{\_}{4}},\frac{1}{2},\underset{\_}{\frac{1}{4}},\underset{\_}{1}\right\}$

$\text{x}(\text{n}){}_4=\left\{\frac{1}{1},\frac{3}{4},\frac{1}{2},\frac{1}{4}\right\}$

$\text{x}(\text{n}){}_4=\left\{\frac{1}{4},\frac{1}{1},\frac{3}{4},\frac{1}{2}\right\}$

$\text{x}(\text{n}){}_4=\left\{\frac{1}{2},\frac{1}{4},\frac{1}{1},\frac{3}{4}\right\}$