Question

What is the term to term rule for the sequence 4,12,36,108,324

Answer 1

Seems to be a geometric sequence

each term is 3 times the previus

$a_n=a_1(r)^{n-1}$
$a_n$ is the nth term
$a_1$ is the first term
r is the comon ratio
n=which term


so first term is 4 and the common ratio is 3 so

$a_n=4(3)^{n-1}$

so the formula is
$a_n=4(3)^{n-1}$ or in other notation
$f(n)=4(3)^{n-1}$

Answer 2

A(n) = a(n-1)*3

There is a common ratio of 3 among the terms.