I'm doing homework and getting stuck at this problem

I'm confused with the concept of induction and I don't know how to do this

a) Prove by induction that 5^n + 2.3^(n+1) + 1 is divisible by 4 for all n ∈ N.

b) Prove that if 2^x = 5 then x is irrational.

any idea guys ?

Thanks,