The summation expression in the following series has an absolute value in it. expand and evaluate the summation notation. what is the sum of the series?

We have that , which means reduces to when , or reduces to when .

So we can expand the summation as



Notice that the 10 contributes a total of 30 from the first sum, and -30 from the second sum, so those terms cancel, leaving us with

25% increaseplus i think decrease i only know increase: ((