Someone help me find the recursive and iterative rules for these sequences?

Geometric Sequence:
4, 8, 16, 32, 64,...
(Representing a population of bacteria that doubles every hour; initial population of 4.)

Arithmetic Sequence:
50, 54, 58, 62, 66,...
(Representing a toll booth that charges $4 per car with an initial amount of $50 in their cash register.)

Question

Someone help me find the recursive and iterative rules for these sequences?

Geometric Sequence:
4, 8, 16, 32, 64,...
(Representing a population of bacteria that doubles every hour; initial population of 4.)

Arithmetic Sequence:
50, 54, 58, 62, 66,...
(Representing a toll booth that charges $4 per car with an initial amount of $50 in their cash register.)

anonymous · Answer

iterative rule like $a_1=2, a_n=2a_{n-1}$  ?

anonymous · Answer

actually for your first example it would be exactly that, only with $a_1=4$

anonymous · Answer

i think that is what it means, does that sound right?  the rule would be 
$$a_1=4,a_n=2\times a_{n-1}$$

anonymous · Answer

second one is similar, but with addition 
$$a_1=50,a_n=a_{n-1}+4$$

anonymous · Answer

Yep! That sounds perfect! Thanks!

anonymous · Answer

yw