<p>已知数列<img src="https://file.gaojiufeng.cn/learnAppQuestion/cc/71/cc713929ff5372abf30d09b0f5acfc31.jpg" style="width: 100%;height: auto;">中，<img src="https://file.gaojiufeng.cn/learnAppQuestion/de/27/de275caf80d744baa32819d7da830abd.jpg" style="width: 100%;height: auto;">是它的前<img src="https://file.gaojiufeng.cn/learnAppQuestion/2e/78/2e78f7b6c4f0a547a620b878129fb456.jpg" style="width: 100%;height: auto;">项和，并且<img src="https://file.gaojiufeng.cn/learnAppQuestion/24/c4/24c44cf0381bb32c810590fbb725df31.jpg" style="width: 100%;height: auto;">设<img src="https://file.gaojiufeng.cn/learnAppQuestion/1e/60/1e607f09567c81267e5254c6bf80c646.jpg" style="width: 100%;height: auto;">求证：数列<img src="https://file.gaojiufeng.cn/learnAppQuestion/dd/dc/dddc7144fa053a10effe1b26fd686414.jpg" style="width: 100%;height: auto;">是等比数列；</p>