The sequence of numbers fff$a_1,a_2,a_3,...,a_n...$/fffis defined byfff\(a

GRE®

登录注册

Question 9 Selected one answer choice

笔记

反馈

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

The sequence of numbers

$a_1,a_2,a_3,...,a_n...$ is defined by

$a_n=\frac{1}{n}-\frac{1}{n+2}$ for each integer n≥1.What is the sum of the first 20 terms of this sequence?

A. $(1+\frac{1}{2})-\frac{1}{20}$

B. $(1+\frac{1}{2})-(\frac{1}{21}+\frac{1}{22})$

C. $1-(\frac{1}{20}+\frac{1}{22})$

D. $1-\frac{1}{22}$

E. $\frac{1}{20}-\frac{1}{22}$

我的答案：

免费解锁Official71-75真题

(Official1-70可直接使用)

扫码添加助教微信

回复关键词“解锁真题”

即可免费解锁！