已知函数<img src="https://static.zxtiku.com/wangke/imgs/topic/9ac8a4d434e99761a2c5622f597a3247.png"/>在任意点<img src="https://static.zxtiku.com/wangke/imgs/topic/10932efc026c0328c6206105a14c200e.png"/>处的增量<img src="https://static.zxtiku.com/wangke/imgs/topic/29fa56babb101a76c8842cf9632bed73.png"/>,且<img src="https://static.zxtiku.com/wangke/imgs/topic/d67045303cdcf65dae2e90ac7e646bba.png"/>,则<img src="https://static.zxtiku.com/wangke/imgs/topic/13dd6cbaa2051bfa022904faf9383600.png"/>等于（）.