\(\left(1-\frac{1}{3}\right).\left(1-\frac{1}{6}\right).\left(1-\frac{1}{10}\right)...\left(1-\frac{1}{190}\right)\)
\(=\frac{2}{3}.\frac{5}{6}.\frac{9}{10}...\frac{189}{190}\)
\(=\frac{4}{6}.\frac{10}{12}.\frac{18}{20}...\frac{378}{380}\)
\(=\frac{1.4}{2.3}.\frac{2.5}{3.4}.\frac{3.6}{4.5}...\frac{18.21}{19.20}\)
\(=\frac{1.2.3...18}{2.3.4...19}.\frac{4.5.6...21}{3.4.5...20}\)
\(=\frac{1}{19}.\frac{21}{3}\)
\(=\frac{1}{19}.7=\frac{7}{19}\)
\(\left(1-\frac{1}{3}\right).\left(1-\frac{1}{6}\right).\left(1-\frac{1}{10}\right)...\left(1-\frac{1}{190}\right)\)
\(=\frac{2}{3}.\frac{5}{6}.\frac{9}{10}....\frac{189}{190}\)
\(=\frac{4}{6}.\frac{10}{12}.\frac{18}{20}....\frac{378}{380}\)
\(=\frac{1.4}{2.3}.\frac{2.5}{3.4}.\frac{3.6}{4.5}....\frac{18.21}{19.20}\)
\(=\frac{1.2.3....18}{2.3.4....19}.\frac{4.5.6...21}{3.4.5....20}\)
\(=\frac{1}{19}.\frac{21}{3}\)
\(=\frac{1}{19}.7=\frac{7}{19}\)
Ủng hộ mk nha !!! ^_^
