3x (1x2+2X3+3x4...+99x100)=
问题描述:
3x (1x2+2X3+3x4...+99x100)=
答
15903
答
=1-1/2 1/2-1/3 1/3-1/4 …… 1/100-1/101 =1-1/101 =101分之100 原式=1-1/2 1/2-1/3 1/3-1/4 . 1/99-1/100
答
99x100x101
答
504900