Ta có:
(1-1/2).(1-1/3).(1-1/4)...........(1-1/10)
=1/2.2/3.3/4............9/10
=1/10
\(\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right)....\left(1-\frac{1}{10}\right)\)
\(=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.....\frac{9}{10}\)
\(=\frac{1.2.3....9}{2.3.4....10}=\frac{1}{10}\)
thanks kb vs mik di de mik nho ban giup do