有关<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/93e05ed10c814657a5670c20ae0fa316.png?x-oss-process=image/sharpen,200"/>的拉普拉斯变换<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/0e7758524c7c46b8aa5e35ce231f5fb5.png?x-oss-process=image/sharpen,200"/>，描述不正确的是（）。