f(x)在x处可导，a，b为常数，则<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/c99d61d2e5794f1fa84c0ccecb689f9f.png?x-oss-process=image/sharpen,200"/><img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/de93b3cc0e6d4c1f84cb6c836bd50f3f.png?x-oss-process=image/sharpen,200"/>=