1/(1x2)+1/(2x3)+1/(3x4)...+1/n(n+1)
1/1x2+1/2x3+1/3x4+1/24x25
1/1x2+ 1/2x3+1/3x4+1/24x25
\(\dfrac{1}{1\times2}+\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+....+\dfrac{1}{24\times25}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{24}-\dfrac{1}{25}\)
\(=1-\dfrac{1}{25}\)
\(=\dfrac{24}{25}\)
1/1x2+1/2x3=1/3x4+...+1/n(n+1)=2013/2014
tìm n
\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{n\left(n+1\right)}=\frac{2013}{2014}\)
\(\Rightarrow1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{n}-\frac{1}{n+1}=\frac{2013}{2014}\)
\(\Rightarrow1-\frac{1}{n+1}=\frac{2013}{2014}\)
\(\Rightarrow\frac{1}{n+1}=1-\frac{2013}{2014}\)
\(\Rightarrow\frac{1}{n+1}=\frac{1}{2014}\)
\(\Rightarrow n+1=2014\)
\(\Rightarrow n=2014-1\)
\(\Rightarrow n=2013\)
1/1x2+1/2x3+1/3x4+......................+1/nx(n+1)<2018/2017
cac cau tu di ma lam bai tap cua minh
cau len mang di , bai nay mk chua hoc , sory nha
chuc ban hoc tot ^-^
tính A = 1x2 + 2x3 +3x4 +... +n x (n +1)
(1/(1x2)/(2x3)/(3x4)):(1/(2x3)/(3x4)/(4x5)):...(1/(97*98)/(98*99)/(99*100))
(1/(1x2)/(2x3)/(3x4)):(1/(2x3)/(3x4)/(4x5)):...(1/(97*98)/(98*99)/(99*100
haizzz đáng tiếc tôi muốn ns là: ko bao f và đừng mong chờ OK
1/(1x2)/(2x3)/(3x4)):(1/(2x3)/(3x4)/(4x5)):...(1/(97*98)/(98*99)/(99*100
(1/(1x2)/(2x3)/(3x4)):(1/(2x3)/(3x4)/(4x5)):...(1/(97*98)/(98*99)/(99*100
Lên Qanda mà hỏi
(1/(1x2)/(2x3)/(3x4)):(1/(2x3)/(3x4)/(4x5)):...(1/(97*98)/(98*99)/(99*100))