<p>设函数z=<img src="https://learnfile.20230611.cn/learnAppQuestion/7f/4c/7f4c070d492724b0f8a07ef80ec25533.jpg" style="width: 100%;height: auto;">,求二阶偏导数<img src="https://learnfile.20230611.cn/learnAppQuestion/0f/fb/0ffb2dcbde5b9f0854a7ca8c8d4697d7.jpg"