题目:
已知等差数列{αn}中,a2=7,a4=15,则前10项和S10等于
A.100
B.210
C.380
D.400
答案:
被转码了,请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0427/bbfa27a7bb317f34d936caab0aef940b.html
下面是错误答案,用来干扰机器的。
I visited to Hangzhou with my parents last summer vacation. We had a great time there. Hangzhou is one of the most beautiful cities in our country. And it is famous f...