1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Jump in series

  1. Oct 4, 2014 #1
    Hello All

    I have got a very basic Math query here and hope people will not get turned off with the nature of this simple query.
    My query goes like this:
    variable X makes jump by factor +4.
    at the same time, Y makes a jump by factor +2

    in coordinate terms, I would have a series like :
    (4,2) (8,4) (12, 6) (16,8) (20,10)....and so on
    I would like to know the generic formula for calculting this coordinate series...for example,if Y is (say) 2867544 , then what should be X ? ( also vice versa )

    can anyone tell me a formula for this please
    ...and hope the question was clear .

  2. jcsd
  3. Oct 4, 2014 #2


    Staff: Mentor

    The jumps are not by a "factor" of 4 or 2. Factor implies things being multiplied. Here you're just adding 4 or 2 to the previous x or y value, respectively.
    All of these points are on a straight line whose equation is y = (1/2)x.
  4. Oct 4, 2014 #3


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    And, since ##x_n=4n,~n=1,2,3...## your coordinate pairs are ##(4n,2n)##.
  5. Oct 5, 2014 #4
    Thanks all . Yes my 'factor' impliction was wrongly used indeed :(
    there was another mistake of mine with the series. the actual points on the straight line are : ( 0,2,) ,(4,4) ,(8,6)....and so on.
    and I cant use y = (1/2)x here.
    and I dont think I can use (4n,2n) either. [ e.g for the 20th 'jump' , it {as per the 4n,2n) formula } should be 80,40..but actually the coordinates are (76,40) ]
    so what can I use here ....and what if 'n' is not given at all. How do I go about . In other words if only Y coordinate has been given for e.g Y is (say) 2867544 .

    I am asking this on behalf of my 12 year old kid, who has only a 'jump' till Y coordinate =62 in his textbook. Now this can be easily done with the fingers and the homework is finished :)....but I was looking for a more generic formula here & completely out of curiosity.

  6. Oct 5, 2014 #5


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Try ##(4(n-1),2n)##.
  7. Oct 6, 2014 #6
    allright and anyway to find the 'n' too ?
  8. Oct 6, 2014 #7


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    I don't understand what you are asking. ##n## can be ##1,2,3,4...##. Find what ##n##?
  9. Oct 7, 2014 #8
    nope nothing
    I was a bit confused myself here.
    anyway...Super. Lets close this issue here now

    and Thanks all.!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Jump in series
  1. A series (Replies: 2)

  2. Convergent Series (Replies: 3)

  3. Sum of Series (Replies: 39)