# How do you find a_1 for the geometric series with r=3 and s_6=364?

If the first term of the series is some $a$, then the equation we have is,
$a \setminus \times {r}^{5} = 364$
$a \setminus \times 243 = 364$ (substitute $r = 3$)
$a = \setminus \frac{364}{243}$