<p>设二元函数<img src="https://learnfile.20230611.cn/learnAppQuestion/d4/1b/d41bdc7e6df06912ccd0e00ce14e9c8b.jpg" style="width: 100%;height: auto;">则<img src="https://learnfile.20230611.cn/learnAppQuestion/68/97/689741ff398be1f61cbc73026cbba4fb.jpg" style