<p>已知<img src="https://learnfile.20230611.cn/learnAppQuestion/3e/39/3e39eeba58c51e56295928d84a70da5d.jpg" style="width: 100%;height: auto;">数列的前<img src="https://learnfile.20230611.cn/learnAppQuestion/25/df/25df2e404a850a9400377bbf88416004.jpg" style