2A = 2/1.2.3 + 2/2.3.4 +.......+ 2/2014.2015.2016
2A = 1/1.2 - 1/2.3 + 1/2.3 - 1/3.4 + 1/3.4 - 1/4.5 +.......+ 1/2014.2015 - 1/2015.2016
2A = 1/1.2 - 1/2015.2016
2A = ................Tự tính rồi tự làm nốt!
\(A=\frac{1}{1x2x3}+\frac{1}{2x3x4}+\frac{1}{3x4x5}+.....+\frac{1}{2014x2015x2016}\)
So sánh A với \(\frac{1}{4}\)
1/1x2x3 + 1/2x3x4 + ... + 1/98x99x100
cho A=1/1x2x3+1/2x3x4+...+1/18x19x20. CMR:A<1/4
3x - (1/1x2+1/2x3+.....+1/99x100)=1/1x2x3+1/2x3x4+......+1/18x19x20
1/1x2x3+1/2x3x4+1/3x4x5+....+1/48x49x50
cho tui đáp án là dc
gấp lămm
Tính 1/1x2x3+ 1/ 2x3x4 + 1/3x4x5 + 1/ 5x6x7 + ...............+ 1/ 35x36x37
Tính :
a) 1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+.....+1
b)1/1x2x3+1/2x3x4+1/3x4x5+.....+1/98x99x100
Tính :
a) 1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+.....+1
b)1/1x2x3+1/2x3x4+1/3x4x5+.....+1/98x99x100
Tính B= 1x2x3 + 2x3x4 + ... + (n-1)n(n+1)
Gấp nha
