Math Help - Factorials

1. Factorials

Hello everyone. Is the an easier way to I evaluate a factorial like the following without writing every number out and canceling.

20!9!
7!21!

Thanks

2. Re: Factorials

Originally Posted by troe
Hello everyone. Is the an easier way to I evaluate a factorial like the following without writing every number out and canceling.

20!9!
7!21!

Thanks
$\frac{20!}{21!}\frac{9!}{7!}= \frac{20!}{21(20!)}\frac{9(8)7!}{7!}$