Question

N = \(\frac{1}{1\times5}+\frac{1}{5\times10}+\frac{1}{10\times15}+\frac{1}{15\times20}+...+\frac{1}{2005\times2010}\)

Tìm số N.

^{Nhankk nkaa minkk t i c k , à maa minkk ckỉ tickk ckoo 5 bạn có câu trả lời đầy đủ và nhank nkất nkaa <3} 

Answer 1

*Mình không chép đề bài nka

\(N=\frac{4}{1.5}\)\(+\frac{4}{5.10}\)\(+\frac{4}{10.15}\)\(+\frac{4}{15.20}\)\(+...+\frac{4}{2005.2010}\)

\(N=1-\frac{1}{5}\)\(+\frac{1}{5}\)\(-\frac{1}{10}\)\(+\frac{1}{10}\)\(-\frac{1}{15}\)\(+\frac{1}{15}\)\(-\frac{1}{20}\)\(+...+\frac{1}{2005}\)\(-\frac{1}{2010}\)

\(N=1-\frac{1}{2010}\)

\(N=\frac{2009}{2010}\)

#Tường Vy ( Ninh Nguyễn )

Answer 2

N = \(\frac{1}{1}-\frac{1}{5}+\frac{1}{5}-\frac{1}{10}+\frac{1}{10}-\frac{1}{15}\)\(+\frac{1}{15}-\frac{1}{20}+.....+\frac{1}{2005}-\frac{1}{2010}\)

N = 1 - \(\frac{1}{2010}\)

N = \(\frac{2009}{2010}\)

Answer 3

\(N=\frac{1}{1\times5}+\frac{1}{5\times10}+\frac{1}{10\times15}+.....+\frac{1}{2005\times2010}.\)

\(N=\frac{1}{1\times5}+\frac{1}{5}\left(\frac{1}{1\times5}+\frac{1}{5\times10}+\frac{1}{10\times15}+.....+\frac{1}{2005\times2010}\right)\)

\(N=\frac{1}{1\times5}+\frac{1}{5}\left(1-\frac{1}{5}+\frac{1}{5}-\frac{1}{10}+\frac{1}{10}-\frac{1}{15}+......+\frac{1}{2005}+\frac{1}{2010}\right)\)

\(N=\frac{1}{1\times5}+\frac{1}{5}\left(1-\frac{1}{2010}\right)\)

\(N=\frac{1}{1\times5}+\frac{1}{5}\left(\frac{2009}{2010}\right)\)

\(N=\frac{1}{1\times5}+\frac{2009}{10050}\)

\(N=\frac{4019}{10050}\)

Answer 4

N = \(\frac{1}{1x5}\) + \(\frac{1}{5x10}\) + \(\frac{1}{10x15}\) + \(\frac{1}{15x20}\) + ...... +  \(\frac{1}{2005x2010}\)

N =  1  -  \(\frac{1}{2010}\)

N  =  \(\frac{2009}{2010}\)

~ Hok T ~

Answer 5

= 2009 / 2010

k mk nha

~ t ~

Answer 6

N =\(\frac{1}{5}-\frac{1}{10}+\frac{1}{10}-\frac{1}{15}\)\(+\frac{1}{15}-\frac{1}{20}+......+\frac{1}{2005}-\frac{1}{2010}\)

N = \(\frac{1}{5}-\frac{1}{2010}\)

N = \(\frac{401}{2010}\)

Answer 7

\(\frac{2009}{2010}\)nha bạn

~HT~

Answer 8

\(N=\frac{1}{1\times5}+\frac{1}{5\times10}+\frac{1}{10\times15}+...+\frac{1}{2005\times2010}\)

\(=\frac{1}{5}\times\left(\frac{5}{1\times5}+\frac{5}{5\times10}+\frac{5}{10\times15}+...+\frac{5}{2005\times2010}\right)\)

\(=\frac{1}{5}\times\left(1-\frac{1}{5}+\frac{1}{5}-\frac{1}{10}+\frac{1}{10}-\frac{1}{15}+...+\frac{1}{2005}-\frac{1}{2010}\right)\)

\(=\frac{1}{5}\times\left(1-\frac{1}{2010}\right)\)

\(=\frac{1}{5}\times\frac{2009}{2010}=\frac{2009}{10050}\)

Answer 9

Câu trả lời của mình bị sai... 

Bạn tham khảo câu trả lời của bạn Nguyễn Ngọc Trúc Mai.