@Seraphus
3n(n+1)(n-1)
Distributed:
3n(n+1) = 3n2+3n, then multiply by (n-1)
OR
3n(n-1) = 3n2-3n, then multiply by (n+1)
Mistake: you distributed to both; it is not (3n)2
When we FOIL it:
(3n2+3n)(n-1) = 3n3 -3n2 +3n2 -3n, which then simplifies to 3n3-3n (since -3n2 +3n2 cancels out)
n2-1...