Odpowiedzi

2009-11-22T19:48:47+01:00
(n-1)!*n*(n+1)*(n+2)/(n-1)!=n*(n+1)*(n+2)
2009-11-22T19:50:40+01:00
2009-11-22T20:00:31+01:00
(n+2)!/(n-1)!= [(n-1)!n(n+1)(n+2)]/(n-1)!=n(n+1)(n+2)=n(n²+3n+2)=
=n³+3n²+2n