Answer:
The first term of the sequence is -120.
Explanation:
The formula for the "nth" term of a geometric sequence is shown below:
an = a0*r^(n-1)
Where an is the nth term, r is the ratio and n is the position of the term on the sequence. For this problem we want to find what is the initial term, a0, so we will isolate it in the formula as shown below:
a0*r^(n-1) = an
a0 = an/[r^(n-1)]
We then apply the data given to us
a0 = 31.45728/[-0.8^(7-1)]
a0 = 31.45728/[-0.8^6] =31.45728 /-0.262144= -120
The first term of the sequence is -120.