Evaluate the related series, of each sequence
-9,-16,-23,-30,-37,-44

We have an arithmetic progression:

An arithmetic progression is a sequence of numbers such that the diference between the consecutive terms is constant.

Explicit formula:
an=a₁+(n-1)*d

a₁ is the first term
d is de common diference
n is the numbers of terms

In this case:
a₁=-9
d=an-an-1=a₂-a₁=-16-(-9)=-16+9=-7

an=-9+(n-1)*(-7)
an=-9-7n+7
an=-7n+-2

a₁=-7*1-2=-9
a₂=-7*2-2=-14-2=-16
a₃=-7*3-2=-21-2=-23
a₄=-7*4-2=-28-2=-30
a₅=-7*5-2=-35-2=-37
a₆=-7*6-2=-42-2=-44