Tích \(\frac{1}{{2019!}}{\left( {1 - \frac{1}{2}}...

C

- Hướng dẫn giải

\(\frac{1}{{2019!}}{\left( {1 - \frac{1}{2}} \right)^1}.{\left( {1 - \frac{1}{3}} \right)^2}...{\left( {1 - \frac{1}{{2019}}} \right)^{2018}} = \frac{1}{{2019!}}.{\left( {\frac{1}{2}} \right)^1}.{\left( {\frac{2}{3}} \right)^2}...{\left( {\frac{{2018}}{{2019}}} \right)^{2018}}\)

\( = \frac{1}{{2019!}}.\frac{{1.2.3...2018}}{{{{2019}^{2018}}}} = \frac{1}{{{{2019}^{2019}}}} = {2019^{ - 2019}}\)

Khi đó (a;b) là (2019;- 2019)