\(B=1+\frac{1}{2}.\frac{2.3}{2}+\frac{1}{3}.\frac{3.4}{2}+\frac{1}{4}.\frac{4.5}{2}+.....+\frac{1}{20}.\frac{20.21}{2}\)
\(B=\frac{2}{2}+\frac{2.3:2}{2}+\frac{3.4:3}{2}+.....+\frac{20.21:20}{2}\)
\(B=\frac{2}{2}+\frac{3}{2}+\frac{4}{2}+\frac{5}{2}+....+\frac{21}{2}\)
\(B=\frac{2+3+.....+21}{2}\)
\(B=\frac{\left(2+21\right).20}{2}:2=\frac{230}{2}:2=165:2=\frac{165}{2}\)
tính B= \(1+\frac{1}{2}.\left(1+2\right)+\frac{1}{3}.\left(1+2+3\right)+\frac{1}{4}.\left(1+2+3+4\right)+...+\frac{1}{20}.\left(1+2+..+20\right)\)
TÍNH B=\(1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+\frac{1}{4}\left(1+2+3+4\right)+...+\frac{1}{20}\left(1+2+3+4+...+20\right)\)
Tính \(B=\frac{1}{2\left(1+2\right)}+\frac{1}{3\left(1+2+3\right)}+\frac{1}{4\left(1+2+3+4\right)}+...+\frac{1}{20\left(1+2+3+...+20\right)}\)
Tính:
\(B=1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+\frac{1}{4}\left(1+2+3+4\right)+...+\frac{1}{20}\left(1+2+3+...+20\right)\)
Tính:
B= \(1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+\frac{1}{4}\left(1+2+3+4\right)+...+\frac{1}{20}\left(1+2+3+...+20\right)\)
Tính:
\(B=1+\frac{1}{2\left(1+2\right)}+\frac{1}{3\left(1+2+3\right)}+\frac{1}{4\left(1+2+3+4\right)}+...+\frac{1}{20\left(1+2+3+...+20\right)}\)
B = \(1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+\frac{1}{4}\left(1+2+3+4\right)+....+\frac{1}{20}\left(1+2+3+...+20\right)\)
thực hiện phép tính 1 cách hợp lý
\(B=1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+\frac{1}{4}\left(1+2+3+4\right)+...+\frac{1}{20}\left(1+2+3+...+20\right)\)
\(\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)\left(1-\frac{1}{4}\right).....\left(1-\frac{1}{n+1}\right)\left(n\in N\right)\)
\(1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+\frac{1}{4}\left(1+2+3+4\right)+.......+\frac{1}{20}\left(1+2+3+4....+20\right)\)
