CPM Homework Help : PC3 Problem 13-36

Calculate the sum of each series, if it exists.

$\displaystyle \sum _ { n = 1 } ^ { \infty } \frac { 4 } { 9 } ( 7 ) ^ { n - 1 }$

Hint:

These are all geometric series. Two are infinite, one is not.

More Help:

$S_n=\frac{a(1-r^n)}{1-r}\text{ for }|r|<1$

$S=\frac{a}{1-r}\text{ for }|r|<1$