I am trying to solve 2 recurrence equations:

a) $a\_{n+1} = 2a\_n + 2^n + 3, a(0)=4$

b) $a\_{n+2} = a\_n + 4n, a(0)=1, a(1)=1$

For (a), I don't know how to deal with $2^n$ part.

For (b), I am confused because $a(0)=a(1)$.