| 1. In each case, apply the formula | ( |
n | ) | = |
n! | and then simplify the resulting fraction (before you multiply anything out). |
| r | r! (n-r)! |
| a) | ( |
9 | ) | = |
9! | = |
9 · 8 · 7 · 6! | = |
3 · 4 · 7 | = |
84. |
| 3 | 3! 6! | 3 · 2 · 1 · 6! |
| b) | ( |
200 | ) | = |
200! | = |
200 · 199 · 198! | = |
100 · 199 | = |
19900. |
| 198 | 198! 2! | 198! · 2 · 1 |