Question

Express the series using sigma notation. -8 + 4 - 2 + 1.

Answer 1

Answer:

-12

Step-by-step explanation:

I believe you want the "sum of the series," because that's what you get from "sigma notation."  Two cases here:  infinite series and partial series.

If you wish to find the sum of the infinite series whose first term is a = -8 and whose common ratio is r = (-1/2), use the formula

                                             a

sum of infinite series = -------------

                                          1 -  r

which here comes to

                                              -8

sum of infinite series = ----------------- = -8/(3/2) = -12

                                         1 - (-1/2)

Answer 2

$\bf -8~~,~~\stackrel{-8\left( -\frac{1}{2} \right)}{4}~~,~~\stackrel{4\left( -\frac{1}{2} \right)}{-2}~~,~~\stackrel{-2\left( -\frac{1}{2} \right)}{1}~\hspace{8em}{\displaystyle\sum\limits_{i=1}^{4}}~-8\left( -\frac{1}{2} \right)^{i-1}$