S= 1/1.3 + 1/3.5 + 1/5.7 +................+ 1/200.202
=>S=1/2.(2/1.3+2/3.5+2/5.7+...+2/200.202)
=>S=1/2.(3-1/1.3+5-3/3.5+...+202-200/200.202)
=>S=1/2.(1-1/3+1/3-1/5+...+1/200-1/202)
=>S=1/2.(1-1/202)
=>S=1/2.201/202
=>S=201/404
Vậy S=201/404
Tính Q =\(\dfrac{1.3}{3.5}+\dfrac{2.4}{5.7}+\dfrac{3.5}{7.9}+...+\dfrac{\left(n-1\right)\left(n+1\right)}{\left(2n-1\right)\left(2n+1\right)}+...+\dfrac{1002.1004}{2005.2007}\)
Cho \(P=\dfrac{2}{1.3}+\dfrac{2}{3.5}+\dfrac{2}{5.7}+...+\dfrac{2}{2019.2021}\)
chứng tỏ rằng P<1
Tìm x biết : \(\dfrac{1}{1.3}+\dfrac{1}{3.5}+\dfrac{1}{5.7}+...+\dfrac{1}{\left(x+2\right).x}=\dfrac{20}{41}\)
Tính tổng các phân số sau
a, 1/18+1/54+1/108+...+1/990
b, 1/1.3+1/3.5+1/5.7+...+1/ 2007.2007
B=\(\dfrac{1}{1.3}\)+\(\dfrac{1}{3.5}\)+\(\dfrac{1}{5.7}\)+...+\(\dfrac{1}{2004.20005}\)
2/1.3+2/3.5+2/5.7+...+2/99.100
a) 1/3-1/4
b) 1/4-1/5
c) S= 1/1.2+ 1/2.3+.........+1/N.(N+1)
d) M= 2/3.5+ 2/5.7+....+ 2/97.99
giải thích cho mik luôn ạ
TínhA:
A=1.3 + 3.5 + 5.7 + ...... + 45.47 + 47.49
3/1.3+3/3.5+3/5.7+.....+3/99.100
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