2. Найдите: 41!/39!, 25!/(23! · 5!).

1. \(\dfrac{41!}{39!}=\dfrac{39!\cdot40\cdot41}{39!}=40\cdot41=1640\).
2. \(\dfrac{25!}{23!\cdot5!}=\dfrac{23!\cdot24\cdot25}{23!\cdot120}=\dfrac{24\cdot25}{120}=5\).

Ответ: 1640; 5.