Tinh : 1x2+2x3+3x4+...+99x100
tinh 1/1x2+1/2x3+1/3x4...1/2005x2006
Tinh: 1/1x2+1/2x3+1/3x4+...+1/99x100
M=1x2+2x3+3x4+4x5+....+99x100
Tính M = 1x2+2x3+3x4+....+212x213
tinh
a)A=1x2+2x3+3x4+............+99x100
b)B=1x3+3x5+5x7+............97x99
c)C=1x2x3+2x3x4+..............98x99x100
s=1x2+2x3+3x4+.........+2020x2021
tính nhanh giá trị biểu thức:a) 1/1x3 + 1/3x5 + 1/5x7 +...+ 1/2007x2009
b) 1/1x2 + 1/2x3 + 1/3x4 +...+ 1/2009x2010
1x2+2x3+3x4+.........2013x2015
