Tuesday, March 31 (Math Lesson)

Today, I will show you how to find the formula for the sum of a geometric sequence.

1. The sum, written out, is: 
2. Then, you multiply r to both sides, getting: 
3. After that, you subtract the second equation from the first, which cancels out all the terms in between the first and last ones, getting:
4. Then, you solve for  getting:, which is the formula!

Weird thing! Quick!