Question

[PHẠM THỊ THÁI HÀ]

Rút gọn biểu thức

A=(1-1/21)(1-1/28)(1-1/36)(1-1/1326)

giúp mk vs!

Answer 1

[soyeon_Tiểu bàng giải]

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

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

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

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

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

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

\(A=\frac{265}{357}\)