Hãy xác định x ( n ) 4 biết X ( k ) = { 3 k = 0 1 1 ≤ k ≤ 3

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

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

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

$x(n){}_4=\left\{\frac{5}{4};1;\frac{3}{4};\frac{1}{2}\right\}$