8.2. Есептеңдер: 1) P₄; 2) P₆; 3) P₇/P₅; 4) P₆/P₈; 5) P₈/P₇ + P₅/P₆; 6) P₉/P₇ − P₇/P₅.

Қайталанбайтын алмастырулар үшін \(P_n=n!\).

1. \(P_4=4!=24\).
2. \(P_6=6!=720\).
3. \(\dfrac{P_7}{P_5}=\dfrac{7!}{5!}=7\cdot6=42\).
4. \(\dfrac{P_6}{P_8}=\dfrac{6!}{8!}=\dfrac{1}{8\cdot7}=\dfrac{1}{56}\).
5. \(\dfrac{P_8}{P_7}+\dfrac{P_5}{P_6}=8+\dfrac{1}{6}=\dfrac{49}{6}\).
6. \(\dfrac{P_9}{P_7}-\dfrac{P_7}{P_5}=9\cdot8-7\cdot6=72-42=30\).

Жауабы: 24; 720; 42; \(\dfrac{1}{56}\); \(\dfrac{49}{6}\); 30.