Posted by haifeng on 2022-11-16 10:18:11 last update 2022-11-16 10:19:38 | Answers (1) | 收藏
证明下面的组合数公式:
(1)
\[C_n^r=\frac{n}{r}C_{n-1}^{r-1}\quad\text{或}\quad\binom{n}{r}=\frac{n}{r}\binom{n-1}{r-1}\]
(2)
\[ C_n^r=\frac{n}{n-r}C_{n-1}^{r}\quad\text{或}\quad\binom{n}{r}=\frac{n}{n-r}\binom{n-1}{r} \]
