2. Evaluate the geometric series given a = -120, r = 0.5 and n = 6

Here we're discussing the "nth partial sum of a geom series."

                                                       1 - r^n

The formula for that is s(n) = a(1)  

                                                         1-r

We can subst. the given values and see where that takes us:

                  1 - (-2)^6        1 - 64

105 = a(1)* = *a(1)  =  -21*a(1)

                    1-(-2)                3

                                              105

Solving this for a(1):  a(1) = = -5    (answer)

                                              -21

its adding 5.5 each time

step-by-step explanation: