\(=4\left(\frac{1}{5.7}+\frac{1}{7.9}+\frac{1}{9.11}+...+\frac{1}{53.55}\right)\)
\(=4\left(\frac{1}{5}-\frac{1}{5}+\frac{1}{7}-\frac{1}{7}+...+\frac{1}{53}-\frac{1}{55}\right)\)
\(=4\left(\frac{1}{5}-\frac{1}{55}\right)\)
\(=4.\frac{2}{11}\)
\(=\frac{8}{11}\)
\(\left(\frac{4}{5.7}+\frac{4}{7.9}+\frac{4}{9.11}+...+\frac{4}{53.55}\right)\)
a,2/5.7 + 2/7.9 + 2/9.11 + ... + 2/53.55
b,1/2 .1/3 +1/4 . 1/5 + ... + 1/8 . 1/9
c,(1+1/2)(1+1/3)(1=1/4).....(1+1/99)
Tính: A = 4/5.7 + 4/7.9 + 4/9.11 + ... + 4/21.23 + 4/23.25
Tính tổng 4/1.3+4/3.5+4/5.7+4/7.9+4/9.11+.....+4/2013.2015
CMR:(2^2/5.7+2^2/7.9+2^2/9.11+...+2^2/53.55)<1
Giúp mk nha:)
Mai nộp rùi]
Thực hiện các phép tính:
j) \(\dfrac{2}{5.7}+\dfrac{2}{7.9}+...+\dfrac{2}{53.55}\)
k) \(\dfrac{1}{2}.\dfrac{2}{3}.\dfrac{3}{4}.\dfrac{4}{5}...\dfrac{99}{100}\)
giúp mình bài này nha,nhanh lên đó,mai là hạn cuối rồi
Đề bài:
4/3.5+4/5.7+4/7.9+4/9.11
tinh nhanh:s=2/5.7+2/7.9+2/9.11+...+2/93.95+3/95.98+4/98.102+5/102.107+2012/107.2119
Tìm x, biết:
x/3.5 + x/5.7 + x/7.9 + x/9.11 + x/11.13 + x/13.15 = 4/45
