Tính:
A=\(\frac{3}{1.2}+\frac{3}{2.3}+\frac{3}{3.4}+...+\frac{3}{99.100}\)
B=1.2.3.4+2.3.4.5+...+97.98.99.100
Tính giúp tớ với, tớ phải nộp rồi\(\frac{3}{1.2.3.4}+\frac{3}{2.3.4.5}+...+\frac{3}{97.98.99.100}\)
tính:
\(\frac{1}{1.2.3.4}+\frac{1}{2.3.4.5}+\frac{1}{3.4.5.6}+...+\frac{1}{97.98.99.100}\)
1.2.3.4+2.3.4.5+...+97.98.99.100
B= 1.2.3.4+2.3.4.5+....+97.98.99.100
Tính tổng S=\(\frac{1}{1.2.3.4}+\frac{1}{2.3.4.5}+...+\frac{1}{n\left(n+1\right)\left(n+2\right)\left(n+3\right)}\)
Tính nhanh \(B=\frac{1}{1.2.3.4}+\frac{1}{2.3.4.5}+...+\frac{1}{n.\left(n+1\right).\left(n+2\right).\left(n+3\right)}\)
Tính Sn biết \(S_n=\frac{1}{1.2.3.4}+\frac{1}{2.3.4.5}+...+\frac{1}{n\left(n+1\right)\left(n+2\right)\left(n+3\right)}\)
Tinh S=1/1.2.3.4+1/2.3.4.5+1/3.4.5.6+...+1/97.98.99.100