Các câu hỏi tương tự
Tính\(\frac{-3}{1\cdot2\cdot3}+\frac{-3}{2\cdot3\cdot4}+\frac{-3}{3\cdot4\cdot5}+...+\frac{-3}{18\cdot19\cdot20}\)
B=\(\frac{1}{1\cdot2\cdot3}+\frac{1}{2\cdot3\cdot4}+...+\frac{1}{18\cdot19\cdot20}\)giải nhanh giùm mình nhé!
\(ChoE=\frac{1}{1\cdot2\cdot3}+\frac{1}{2\cdot3\cdot4}+...+\frac{1}{18\cdot19\cdot20}\)
Chứng minh rằng E<\(\frac{1}{4}\)
Tính nhanh :
\(\frac{2}{1\cdot2}\)+ \(\frac{2}{2\cdot3}\)+ \(\frac{2}{3\cdot4}+\frac{2}{4\cdot5}+......+\frac{2}{18\cdot19}+\frac{2}{19\cdot20}\).
Giúp mk nha ai nhanh mk tk
\(A=\frac{1^2}{1\cdot2}\cdot\frac{2^2}{2\cdot3}\cdot\frac{3^2}{3\cdot4}\cdot\cdot\cdot\cdot\cdot\frac{9^2}{9\cdot10}\)
chứng tỏ \(\frac{1}{1\cdot2}+\frac{1}{1\cdot2\cdot3}+\frac{1}{1\cdot2\cdot3\cdot4}+...+\frac{1}{1\cdot2\cdot3\cdot...\cdot100}< 1\)
\(\frac{1}{1\cdot2\cdot3}+\frac{1}{2\cdot3\cdot4}+\frac{1}{3\cdot4\cdot5}+.....+\frac{1}{98\cdot99\cdot100}=\frac{1}{k}\cdot\left(\frac{1}{1\cdot2}-\frac{1}{99\cdot100}\right)\)
Số k trong đẳng thức trên có giá trị là ?
Tìm y :
\(\left(\frac{1}{1\cdot2\cdot3}+\frac{1}{2\cdot3\cdot4}+\frac{1}{3\cdot4\cdot5}+...+\frac{1}{98\cdot99\cdot100}\right)\cdot y=\frac{49}{200}\)
\(\frac{1^2}{1\cdot2}\cdot\frac{2^2}{2\cdot3}\cdot\frac{3^2}{3\cdot4}\cdot\frac{999^2}{999\cdot1000}\)