连续型随机变量<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/5c4e7cddb30c4c6fa9a2262bbc4f3fdd.png?x-oss-process=image/sharpen,200"/>的密度函数为<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/91ee42398e8f4ac1a46a68b09485d376.png?x-oss-process=image/sharpen,200"/>,则<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/286e7f1b3fa94e6bb6bdd084c1283d28.png?x-oss-process=image/sharpen,200"/>（）.