Question

Which of the following is the formula for the geometric sequence?
1, -8, 64, -512, …

Answer 1

Again, the same forumla I said last time...
http://en.wikipedia.org/wiki/Geometric_sequence

64/-8 = -8

Answer 2

these are the answers that are shown????
an=-1(8)n − 1
an=8(-1)n − 1
an=1(-8)n − 1
an=-8(1)n − 1

Answer 3

ah, sorry, I've just solved enough geomentric sequences that were asking for the common ratio that I didn't read carefully enough.

I'm guessing that the n-1 on each of those is a subscript?

If that's true then you should start at 1 because that's where your sequence starts. Then comes your common ratio (-8), and then you have the n-1, which is ALWAYS a way to show how many terms you wanted to solve for (in this case there are 4 terms, but the ... indicates that it goes on infinitely).

\[1(-8)_{n-1}\]

Answer 4

don't forget to medal