Sequences

Find the general term of the following sequences:

a)$7, 13, 19, 25, 31, \ldots$
$a_n=6n+1$

b) $4, –6, 9, -\frac{27}{2}, \ldots$
$a_n=4*(-\frac{3}{2})^{n-1} \\ a_n=a_{n-1}*(-\frac{3}{2})$