Where does one term end and the other begin?

1. Apr 5, 2005

trigger352

I need help determining the explicit formula and writing the series in sigma notation with a specified lower limit.

In both of them, I cannot tell where one term ends and the other begins, or what to do when the sign changes.

Series #1
$$- 2 - 5 - 8 - 11 - 14 - 17 - 20$$; lower limit = $$3$$
Series #2
$$4.4 + 2.4 + 0.4 - 1.6 - 3.6 - 5.6 - 7.6$$; lower limit = $$2$$

2. Apr 6, 2005

chroot

Staff Emeritus
Each term is a number, either positive or negative. Since this is a series, you are implicitly adding all the terms. The terms which are negative get rid of the plus sign before them, per convention.

- Warren