<p>已知直线<img src="https://file.gaojiufeng.cn/learnAppQuestion/66/18/6618411d653bd800b1b8968af8487d24.jpg" style="width: 100%;height: auto;">与直线<img src="https://file.gaojiufeng.cn/learnAppQuestion/cc/ee/ccee4ce7e27809677b46ef6e40f3d43d.jpg" style="width: 100%;height: auto;">互相垂直，则<img src="https://file.gaojiufeng.cn/learnAppQuestion/70/78/7078c62bc70438d1ee1c54e56e5adddf.jpg" style="width: 100%;height: auto;">的值是（）.</p>