5+25+125+625+3125+15625 rewrite each series using sigma notation

1. You have that the series is: 5+25+125+625+3125+15625
 2. You must find the ratio (r) between the adjacent members. Then, you have:

 25/5=5
 125/25=5
 625/125=5
 3125/625=5
 15625/3125=5

 3. Therefore, the ratio is:

 r=5

 4. Then, each term has te form 5^k. So, you have:

 5^1=5
 5^2=25
 5^3=125
 5^4=625
 5^5=3125
 5^6=15625

 5. As you can see, "k" goes from 1 to 6.

 6. The answer is shown in the image attached.