# series or sequence

1. ### Two series/sequence problems

Evening all, two questions here, first off I'm just sceptical with my answer for the first question, in great need of a second opinion in terms of my methods etc. The second question I'm really struggling where to start. Help would be much appreciated! Firstly: The sum of the first four terms...
2. ### geometric series/sequence given question

consider the following geometric sequences and find the terms indicated: *The 1st term is 440 and the 12th is 880. find S6
3. ### Series/Sequence Problem

I'm having a problem with a question The question is: A chemical plant discharges D units of chemical molecules into a river each week. At the end of the week 90% of the chemical molecules have dissipated. a) Find the number of units of the molecule after n weeks: I got this...
4. ### Arithmetic Series/Sequence merger

Im not quite sure how to do this.. I am instructed to find the value of the 11th term of an arithmetic sequence where t1=-13 and the sum of the first 1 terms is -33. Now I thought I could use the equation -33= (-13+tn/2)11 but that is either not the right approach or I am simplifying it...
5. ### Series/Sequence

An = 3n / (12n+15) Series n=1 infinity (An) (Sorry,i dont know the symbols) Does this converge or diverge? if it diverges does it go to infinity or minus infinity? If it converges what would be the limit? Sequence {An} Same question. For the series, i said that it goes to infinity, but im...