\(A=\left(1-\frac{1}{21}\right).\left(1-\frac{1}{28}\right).\left(1-\frac{1}{36}\right).....\left(1-\frac{1}{1326}\right)\)

\(A=\frac{20}{21}.\frac{27}{28}.\frac{35}{36}......\frac{1325}{1326}\)

\(A=\frac{5.8}{6.7}.\frac{6.9}{7.8}.\frac{7.10}{8.9}.....\frac{50.53}{51.52}\)

\(A=\frac{5.\left(6.7.....50\right)}{\left(6.7.....50\right).51}.\frac{53.\left(8.9.10.....52\right)}{7.\left(8.9.10.......52\right)}\)

\(A=\frac{5}{51}.\frac{53}{7}=\frac{265}{357}\)

thong diep nho :

hay kỉ ko muốn

ai tích mình tích lại nha

cha hieu cai gi ca

ai h minh minh h lai

Qui luật kiểu gì vậy hả trời ?!

\(A=\frac{20}{21}\cdot\frac{27}{28}\cdot\frac{35}{36}\cdot...\cdot\frac{1325}{1326}\)

\(=\frac{40}{42}\cdot\frac{54}{56}\cdot\frac{70}{72}\cdot...\cdot\frac{2650}{2652}\)

\(=\frac{5\cdot8}{6\cdot7}\cdot\frac{6\cdot9}{7\cdot8}\cdot\frac{7\cdot10}{8\cdot9}\cdot...\cdot\frac{50\cdot53}{51\cdot52}\)

\(=\frac{5\cdot53}{7\cdot51}=\frac{265}{357}\)

\(\left(1-\frac{1}{21}\right).\left(1-\frac{1}{28}\right).\left(1-\frac{1}{36}\right)...\left(1-\frac{1}{1326}\right)\)

\(=\frac{20}{21}.\frac{27}{28}.\frac{35}{36}...\frac{1325}{1326}\)

\(=\frac{40}{42}.\frac{54}{56}.\frac{70}{72}...\frac{2650}{2652}\)

\(=\frac{5.8}{6.7}.\frac{6.9}{7.8}.\frac{7.10}{8.9}...\frac{50.53}{51.52}\)

\(=\frac{5.6.7...50}{7.8.9...52}.\frac{8.9.10...53}{6.7.8...51}\)

\(=\frac{5.6}{51.52}.\frac{52.53}{6.7}\)

\(=\frac{5.52}{51.7}=\frac{260}{357}\)

Ủng hộ mk nha ^_-

= 265/327 

Ai giúp mình với, cảm ơn nhìu!