画出满足差分方程:y[n]-1.25y[n-1]+0.75y[n-2]-0.125y[n-3]=x[n]+0.5x[n-1]，离散时间信号X[n]的双边z变换是离散傅里叶变换的推广,而离散时间傅里叶变换在研究离散时间信号与系统中是很有用的。

-Drawn to meet the difference equation: y [n]-1.25y [n-1]+ 0.75y [n-2]-0.125y [n-3] = x [n]+ 0.5x [n-1], discrete-time signal X [n] the bilateral z transform is the promotion of discrete Fourier transform, and discrete-time Fourier transform in the study of discrete-time signal and the system would be very useful.