Please help with the below:

Find an expression for the nth term of the given sequence.

a). 3,6, 12,24, ...
b). 151,142,133,124, ...

2 answers

(a) should be easy -- each term is twice as big
Tn = 3/2 * 2^n

(b) each term is 9 less, so
Tn = 160-9n
Thank you.