Đặt A=1/1.2.3+1/2.3.4+...+1/99.100.101
2A=2/1.2.3+2/2.3.4+...2/99.100.101
2A=3-1/1.2.3+4-2/2.3.4+...+101-99/99.100.101
2A=3/1.2.3-1/1.2.3+4/2.3.4-2/2.3.4+...+101/99.100.101-99/99.100.101
2A=1/1.2-1/2.3+1/2.3-1/3.4+...+1/99.100-1/100.101
2A=1/2-1/10100
Tính \(A=\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+.....+\frac{1}{99.100.101}\)
Tính:
f) F= 1.2+2.3+3.4+...+n(n+1)
g) G= 1.2.3+2.3.4+3.4.5+...+99.100.101
h) H= 1.2.3+2.3.4+3.4.5+...+n(n+1)(n+2)
i) I= 1.3+2.4+3.5+...+99.100
j) J= 1.4+2.5+3.6+...+99.102
Tính
\(A=\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+...+\frac{1}{99.100.101}\)
Tính : \(A=1.2.3+2.3.4+3.4.5+.....+99.100.101\)
tinh A=1/1.2.3+1/2.3.4+....+1/99.100.101
Tính
A = \(\frac{1}{1.2.3}-\frac{1}{2.3.4}-.......-\frac{1}{99.100.101}\)
tinh
1/1.2.3+1/2.3.4+....+1/99.100.101
tinh
1/1.2.3+1/2.3.4+.....+1/99.100.101
Tính 1/1.2.3-1/2.3.4-1/3.4.5-.......-1/97.98.99
