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

Prove:

1) 7^2n - 48n -1 for 2304 for n=1,2,3...

2) (3n+1).7^n -1 is divisible by 9 for n=1,2,3...

3) 10^n +3[4^(n+2)] +5 is divisible by 9 for n=1,2,3...

Thank you !