C=1/1.2.3+1/2.3.4+1/3.4.5+...+1/a.(a+1).(a+2)
Cho S=\(\dfrac{5}{1.2.3}+\dfrac{8}{2.3.4}+\dfrac{11}{3.4.5}+...+\dfrac{6068}{2022.2023.2024}\)
So sánh S với 2
Tính \(A=\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+.....+\frac{1}{99.100.101}\)
Tính 1/1.2.3-1/2.3.4-1/3.4.5-.......-1/97.98.99
Tính 1/1.2.3 -1/2.3.4 -1/3.4.5- .....-1/97.98.99
tính: \(\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+...+\frac{1}{a\left(a+1\right)\left(a+2\right)}\)
Tính: 1/1.2.3+1/2.3.4+1/3.4.5+...+1/99.100.101
Tính nhanh tổng sau: 1/1.2.3+1/2.3.4+1/3.4.5+...+1/10.11.12
1/1.2.3+1/2.3.4+1/3.4.5+...+1/18.19.20
help me please:))))) thanks