сократите дробь (n+20)!/(n+1)(n-1)!

Question

сократите дробь (n+20)!/(n+1)(n-1)!

Answer 1

   (n+20)!         (n-1)! n *(n+1)(n+2)...(n+20)

--------------- = ---------------------------------------- =  n(n+2)(n+3)(n+4)...(n+20)

(n+1)(n-1)!                   (n+1)(n-1)!