CHỨNG MINH 1/2-1/3+1/4-1/5+1/6-1/7+....+1/2012-1/2013+1/2014 < 2/5
cho A=1*4/2*3 + 2*5/3*4+3*6/4*5+.....+2013*2016/2014*2015 . Chứng minh 2012< A < 2013
chứng minh\(\frac{1}{2}-\frac{1}{3}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{2012}-\frac{1}{2013}+\frac{1}{2014}< \frac{2}{5}\)
chứng minh \(\frac{1}{2}-\frac{1}{3}+\frac{1}{4}-\frac{1}{5}+....+\frac{1}{2012}-\frac{1}{2013}+\frac{1}{2014}< \frac{2}{5}\)
1/1*2+1/3*2+1/5*6+.....+1/2013*2014
-------------------------------------------------------
1/1008*2014+1/1009*2013+1/1010*2012+....1/2014*2018
tính
A=1+1/2(1+2)+1/3(1+2+3)+1/4(1+2+3+4)+...+1/2013(1+2+3+4+...+2013)
B=(1-3)/(1.3)+(2-4)/(2.4)+(3-5)/(3.5)+(4-6)/(4.6)+...+(2011-2013)/(2011.2013)+(2012-2014)/(2012.2014)-(2013+2014)/(2013.2014)
thứ 7 mình nộp ai làm nhanh mình tích cho
nhớ giải chi tiết
(1/2012+1/2013-1/2014)/(5/2012+5/2013-5/2014)-(2/2103+2/2014-2/2015)/(3/2013+3/2014-3/2015)
Thực hiện tính :
a) A = 1+1/2(1+2)+1/3(1+2+3)+1/4(1+2+3+4)+...+1/2013(1+2+3+..+2013)
b) B = 1-3/7.3+2-4/2.4+3-5/3.5+4-6/4.6+....+2011-2013/2011.2013+2012-2014/2012.2014-2013+2014/2013.2014
S-1+2+3-4-5+6+7+8-9-10+11+12+13-14-15+...+2011+2012+2013-2014-2015
(Tính)
