21C5+21C15=?
express in simple combinations
4 years ago
21C5 can also be written as $\frac{21!}{5!\left(21-5\right)!}$21!5!(21−5)! , which simplifies to $\frac{21!}{5!15!}$21!5!15!
21C15 can also be written as $\frac{21!}{15!\left(21-15\right)!}$21!15!(21−15)! , which simplifies to $\frac{21!}{15!5!}$21!15!5!
4 years ago
Answered By Emily D
21C5 can also be written as $\frac{21!}{5!\left(21-5\right)!}$21!5!(21−5)! , which simplifies to $\frac{21!}{5!15!}$21!5!15!
21C15 can also be written as $\frac{21!}{15!\left(21-15\right)!}$21!15!(21−15)! , which simplifies to $\frac{21!}{15!5!}$21!15!5!