设曲线方程为<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/1dad5f1cd204467db1a20dace464d220.png?x-oss-process=image/sharpen,200"/>则该曲线在点<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/6470fc9982344991a06a456f3aea95a8.png?x-oss-process=image/sharpen,200"/>处的法平面方程为（）．