1⼀1×4+1⼀4×7+1⼀7×10+……+1⼀2017×2020=? 有解题步骤吗?

2025-04-04 06:36:02
推荐回答(1个)
回答1:

1/1×4+1/4×7+1/7×10+……+1/2017×2020
=1/3x(1-1/4+1/4-1/7+...+1/2017-1/2020)
=1/3x(1-1/2020)
1/3x2019/2020
=673/2020