若某因果离散时间系统的系统模拟框图如题26图所示，则系统稳定时<img src="https://static.zxtiku.com/wangke/imgs/topic/1b1a70bc691183fdb83c5c1f47632dba.png"/>值范围是 ( )<br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/5bcd8ad358761bda3588ec1890196138.jpg"/>