Write the recursive formula for the geometric sequence. A^1=-2 A^2=8 A^3=-32
and its not An=-2*an-1
well the first thing i see is it alternates between positive and negative. do you know how to write that?
no
\[\huge (-1)^n\] do you see how we would jump back and forth between -1 and 1?
yes
but on all of my answers it stays -1
Great! now all we need to figure out is how it goes from 2, 8 and then 32.
alright
Is this a multiple choice question or do you have an answer booklet of some sort?
I could be misunderstanding the question. :/
A. an=-4+an-1 B. an=-2+an-1 D. an=-4*an-1
th reason i didnt write c is because its the wrong answer
Ah, i see what we need to do here. http://www.algebralab.org/lessons/lesson.aspx?file=algebra_geoseq.xml We need to find the common ratio and then we'll have our answer. It talks about that in the first paragraph or so on that website.
so we just need to know what we can multiply the first term by that gives us 8 and then that number has to work when multiplying it by 8 to get 32. Does that make sense?
yea
So basically that pattern i was talking about before. Just ignore my (-1)^n stuff. That's for a different representation okay?
So you can setup an equation to figure it out. :D \[\huge -2*x=8\]\[\huge 8*x=-32\] x must be the same number for both answer. give it a try.
Once you find x, your answer will be in the form: \[\huge a_n=a_{n-1}*x\] I hope that all makes sense! :D
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