\(2D=\frac{2}{1.2.3}+\frac{2}{2.3.4}+..+\frac{2}{23.24.25}\)
\(2D=\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-.....-\frac{1}{24.25}=\frac{1}{2}-\frac{1}{600}=\frac{299}{600}\Rightarrow D=\frac{299}{1200}\)
Cho S = 1/1.2.3 + 1/2.3.4 + 1/3.4.5 + ... + 1/23.24.25
Hãy so sánh S với 0,25
\(\frac{1}{1.2.3}+\frac{1}{2.3.4}+....+\frac{1}{23.24.25}\)
cho mình cách giải luôn nha!
Tính S gồm 23 số hạng: \(S=\frac{1}{1.2.3}+\frac{1}{2.3.4}+...+\frac{1}{\left(n-1\right).n.\left(n+1\right)}+...+\frac{1}{23.24.25}\)
3/1.2.3 + 3/2.3.4 + 3/4.5.6 + .... + 3/23.24.25
tính tổng S gồm 23 số hạng :
S = \(\frac{1}{1.2.3}+\frac{1}{2.3.4}+...+\frac{1}{\left(n-1\right).n\left(n+1\right)}+\frac{1}{23.24.25}\)
\(\frac{10^{2017}+9}{10^{2017}-7}\)
\(\frac{1}{4}+\frac{1}{16}+\frac{1}{36}+\frac{1}{64}+\frac{1}{100}+\frac{1}{144}+\frac{1}{196}\)
\(\frac{1}{1.2.3}+\frac{1}{2.3.4}+...+\frac{1}{23.24.25}\)
Tính
1) tính :
a) 2/ 1.2.3 + 2/ 2.3.4 + ...+ 2/ 98.99.100
b) 4/ 2.4.6 + 4/ 4.6.8 + ...+ 4/ 50.52.54
c) 8/ 1.3.5 + 8/ 3.5.7 + ...+ 8/ 18.19.20
d) 1/ 1.2.3 + 1/ 2.3.4 + ... + 1/ 18.19.20
Tính nhanh: D= 1/1.2.3+1/2.3.4 +1/3.4.5+ ..... + 1/98.99.100
P = 1/1.2.3 + 1/2.3.4 + 1/3.4.5 +...+ 1/n(n+1)(n+2)
S = 1/1.2.3 + 1/2.3.4 + 1/3.4.5 +...+ 1/48.49.50 .
