You can put this solution on YOUR website! THE QUESTION IS NOT VERY CLEAR ..
IF IT REALLY MEANS WHAT IS WRITTEN THEN SINCE N IS AN INTEGER N^3-N IS AN INTEGER AND IT IS DIVISIBLE BY N^3-N WHICH IS THE LARGEST INTEGER.IF IT IS NEEDE TO FIND A NUMBER LESS THAN THIS THEN
N^3-N=N(N^2-1)=N(N+1)(N-1)...SO TAKING THE LARGER OF THE 3 FACTORS N(N+1)=N^2+N IS THE LARGEST INTEGER FOR ALL N.