3x (1x2+2X3+3x4...+99x100)=

问题描述:

3x (1x2+2X3+3x4...+99x100)=

15903

=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

99x100x101

504900