Cho   X ( Z ) = Z Z − 2 . Tìm x ( n ) với | Z | < 2 .

$x\left(n\right)=\left(-\frac{1}{2}\right){}^{-n}u\left(-n-1\right)$

$x\left(n\right)=-\left(\frac{1}{2}\right){}^{-n}u\left(-n-1\right)$

$x\left(n\right)=-\left(-\frac{1}{2}\right){}^{-n}u\left(n-1\right)$

$x\left(n\right)=-\left(-\frac{1}{2}\right){}^{-n}u\left(-n-1\right)$