填空题:若向量<img src="http://www.weimei168.com/uploads/202208/161257963461461.png" width="22" height="30" />=(1，k，3)<img src="http://www.weimei168.com/uploads/202208/161257970376641.png" width="14" height="25" />能由向量<img src="http://www.weimei168.com/uploads/202208/161257962132831.png" width="20" height="29" />=(1，-3，2)<img src="http://www.weimei168.com/uploads/202208/161257970376641.png" width="14" height="25" />，<img src="http://www.weimei168.com/uploads/202208/161257962862621.png" width="24" height="29" />=(2，1，-l)<img src="http://www.weimei168.com/uploads/202208/161257970376641.png" width="14" height="25" />线性表示，则k=_______．