Question

Нужно решить комбинирование

Answer 1

1) = (n +2)(n +3) = n² +5n +6
2)( 1/(n+1)! +1/n! ) * n! = (1 + n +1)/((n+1)! *n! = (n+2)/(n+1)
3) a) 1/n! - 1/(n+2)! = ((n+1)(n+2) -1 )/(n+2)! = (n² +3n +2 -1)/(n+2)!=
=(n² +3n +1)/(n+2)!
    б) (n² +3n +1)/(n+2)! * (n+1)! = (n² +3n +1)/(n+2)