Could someone help me with these questions? I just need to prove n=k+1 using the assumption that n=K

Prove:

1) n^3 - n is divisible by 6 for n=2,3,4...

2) n^4 - 1 is divisible by 3 for n=1,2,3...

3) n(n^2 +5) is divisible by 6 for n=1,2,3....

Thank you ! =)