Question 891783
That looks like geometric sequence, {{{r=-2}}}.
The general sequence's term is {{{3*(-2)^(n-1)}}} and n would be the index of the term.


You can think of the sequence this way:
3, 3(-2)^1, 3(-2)^2, 3(-2)^3, 3(-2)^4,....3(-2)^n
This way showing the sequence uses indexing from 0 to n-1.
Sum of the first n terms is {{{highlight(3((1-(-2)^n)/(1-(-2))))}}}.
For reference, other than a good college algebra book, you can see <a href="http://en.wikipedia.org/wiki/Geometric_series">http://en.wikipedia.org/wiki/Geometric_series</a>.