=1/2 x ( 1-1/3+1/3-1/5+1/5-1/7+...+1/2013-1/2015)
=1/2 x ( 1-1/2015 )
=1/2 x 2014/2015
=1007/2015
Đúng 0
Bình luận (0)
Các câu hỏi tương tự
tính :\(\frac{1}{1\times2\times3}+\frac{1}{2\times3\times4}+\frac{1}{3\times4\times5}+\frac{1}{4\times5\times6}+\frac{1}{5\times6\times7}+\frac{1}{6\times7\times8}+\frac{1}{7\times8\times9}+\frac{1}{8\times9\times10}\)
TÍNH NHANH:\(\frac{1}{1\times3\times5}+\frac{1}{2\times5\times8}+\frac{1}{3\times5\times7}+\frac{1}{5\times8\times11}+\frac{1}{5\times7\times9}+\frac{1}{8\times11\times14}+...+\frac{1}{995\times997\times999}+\frac{1}{1493\times1496\times1499}\)
Tính nhanh:
N = \(\frac{1}{1\times3}+\frac{1}{3\times5}+\frac{1}{5\times7}+...+\frac{1}{199\times201}\)
\(\frac{1}{1\times3}+\frac{1}{3\times5}+\frac{1}{5\times7}+...+\frac{1}{17\times19}\)=
Tính nhanh
\(\frac{2}{1\times3}+\frac{2}{3\times5}+\frac{2}{5\times7}+\frac{2}{7\times9}+\frac{2}{9\times11}\)
Tính \(\frac{2}{1\times3}+\frac{2}{3\times5}+\frac{2}{5\times7}+...+\frac{2}{77\times79}\)
\(\left(\frac{1}{1\times3}+\frac{1}{3\times5}+\frac{1}{5\times7}+\frac{1}{7\times9}+\frac{1}{9\times11}\right)\times y=\frac{2}{3}\)
Tìm y
\(\frac{4}{1\times3}+\frac{4}{3\times5}+\frac{4}{5\times7}+...+\frac{4}{11\times13}=?\)
\(\left(\frac{4}{1\times3}+\frac{4}{3\times5}+\frac{4}{5\times7}+\frac{4}{7\times9}\right)\times10-x=0\)