问题: 简单数学题
The sum of the first 6 terms of an arithmetic progression is 96. The sum of the first 10 terms is one third of the sum of the first 20 terms. Find the first term and the common difference.
解答:
解：
S6=3(a1+a6)=6a1+15d=96,a1=16-5d/2
S10=5(a1+a10)=10a1+45d=160+20d
S20=10(a1+a20)=20a1+190d=320+140d
∵S10=S20/3
∴160+20d=320/3+140d/3,d=2
a1=16-5×2/2=11
版权及免责声明
1、欢迎转载本网原创文章，转载敬请注明出处：侨谊留学（www.goesnet.org）；
2、本网转载媒体稿件旨在传播更多有益信息，并不代表同意该观点，本网不承担稿件侵权行为的连带责任；
3、在本网博客/论坛发表言论者，文责自负。
