Use Austin’s method to compute the sum of each series below.

1. $1+5+25+$$125+625+$$3125+15,625$ 

   Hint (a):

   If the given series is $S$, compute $5S − S$.

   More Help (a):

   Did you get $4S = 78{,}124 - 1$?

2. $5+15+$$45+...+885,735$ 

   Hint (b):

   Identify the common ratio, $r$.
   Then, if the given series is $S$, compute $rS − S$.