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Pre calc, domain sets

  1. Aug 24, 2004 #1
    Two functions are said to be equal if they ahve the same domain and, for each value in the domain set, the fucntion values are equal respectively.

    F = {(2,3),(3,4),(4,5)
    G = {(3,4),(4,5),(2,3)

    The domain sets are equal, and f(x) = g(x) for each corresponding value of the domain.

    Tow fucntions f(x) and g(x) may be added together only for equal domain sets.
    Symbolically f(x) + g(x) = (f+g)(x)

    F = {(2,3),(5,7),(8,1),(-2,3)
    G = {(2,5),(6,7),(9,3),(8,6),(-2,3)


    Notice that the equal domain set is
    D = {2,8,-2}

    and the sum of the function values are

    Im just wondering how they figured that out, where the 2,8; 8,7; -2,6 all came from.
    Last edited: Aug 24, 2004
  2. jcsd
  3. Aug 24, 2004 #2
    (f+g)(x)={(2,8),(8,7),(-2,6) is the result of adding the ordinates of the two functions with the same x value (abscissa)

    F = {(2,3),(5,7),(8,1),(-2,3)
    G = {(2,5),(6,7),(9,3),(8,6),(-2,3)

    Look at the 2 functions.

    (2,3) and (2,5) have the same x-value. Hence we add the y-values (because they are common)

    We get (2,8)

    Do this for the other elements in the function sets.
  4. Aug 24, 2004 #3
    Thanks for your help, I figured it out I think!
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