### Home > PC3 > Chapter 12 > Lesson 12.3.2 > Problem12-146

12-146.

Evaluate each of the following sums.

1. $2m+1+3m−$$1+4m−3+\dots+$$25m−45$

This is an arithmetic series with a common difference of $m − 2$.

2. $−4a+2a^3−$$a^5+\dots$

This is a geometric series with a common ratio of $−0.5a^{2}$.