Results 1 to 3 of 3

Math Help - Sequences and Series Help (Grade 11)

  1. #1
    Newbie
    Joined
    Jan 2009
    From
    Canada
    Posts
    2

    Sequences and Series Help (Grade 11)

    Hi guys,

    I have a math assignment here dealing with geometric series/sequences, arithmetic series/sequences, and the recursion formula. The problem is that I don't know which formula applies to which question!

    If you could, a detailed explanation would be really wonderful.

    Here are the questions:

    1. Find tn and t11 for the sequence 6x,12x^2, 24^3...
    (For this one, I use the geometric sequence, right?)

    2. Find s31 for 36+34+32+...

    3. Each year, for 8 years, the population of a city increased by 3.5% of its value in the previous year. If the initial population was 320 000, what was its population by the end of the 8th year?

    4. If a sequence is determined by f(x) = 6^x-1 where x is a natural number, find the sum of the first 15 terms.

    Of course I don't expect anyone to help me with all of them, but even if you helped me figure out which formula to use for any of them, I would be really grateful!

    Thank you so much in advance!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member vincisonfire's Avatar
    Joined
    Oct 2008
    From
    Sainte-Flavie
    Posts
    469
    Thanks
    2
    Awards
    1
    1. You see that the number double every time so you will have something like  2^n As for the x you see that the exponent also increase by 1 each time so that you have  x^n
    2. The term decrease by 2 every time i_n = 38 - n You want  \sum_{n=1}^{31} 38 -n remember that  \sum_{n=1}^i n = \frac{i^2+i}{2} .
    3.  P = P + 0.035 P = 1.035 P That's for one year, the next year 1.035 \cdot (1.035 \cdot P) = 1.035^2 P After n years  P_{tot} = 1.035^n P
    4. Use \sum_{i=0}^n 6^i = \frac{1-6^{n+1}}{1-6} Decompose the sum and use also \sum_{i=0}^n 1 = n
    Last edited by vincisonfire; January 11th 2009 at 04:30 PM.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jan 2009
    From
    Canada
    Posts
    2
    Thank you very much for your help, vincisonfire.

    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 7
    Last Post: July 27th 2010, 10:34 AM
  2. Challenging grade 6 question or grade 9 ?
    Posted in the Algebra Forum
    Replies: 2
    Last Post: June 24th 2010, 11:04 AM
  3. Replies: 1
    Last Post: June 6th 2010, 10:51 PM
  4. Grade 11 help: Sequences
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: November 27th 2008, 07:31 PM
  5. Sequences and Series - Power Series Question
    Posted in the Calculus Forum
    Replies: 3
    Last Post: April 20th 2008, 08:32 PM

Search Tags


/mathhelpforum @mathhelpforum