I need help with my math!!! (Pre-calc)

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  • 71 LS6
    Nick Tahou's guru
    • May 2002
    • 230
    #1

    I need help with my math!!! (Pre-calc)

    Ok, I'm usually pretty good at this stuff, but one problem tonight is really bothering me. For the given functions f(x) and g(x) I need the following:

    Find algebraically f(g(x)) and state the domain.

    f(x) = (x-1)/(x+2) g(x) = 1/x


    When I do it, I get that f(g(x)) = (1/x-1)/(1/x+2)

    This seems correct to me, but according to my graphing calculator (TI-83+) it is not the true representation of the composite f(g(x)), because when the calculator graphs my answer, it does not match the graph that the calculator comes up with if I enter f(x) and g(x) separately and let the calculator calculate and graph the composite by itself.

    I would greatly appreciate it if anyone can help me with this.
    Last edited by 71 LS6; 09-09-2002, 07:02 PM.
    - There's no replacement for displacement.

    "It's not peer pressure, it's just your turn."

    AO Teenage Mutant Ninja Turtle: Donatello
    Tags: None
    • Miscue
      Super Moderator

      • Oct 2000
      • 7105
      #2
      I got:

      1 - x
      ------
      1 + 2x

      If I didn't do it backwards.

        Comment

        • 71 LS6
          Nick Tahou's guru
          • May 2002
          • 230
          #3
          Thanks Miscue, that checks out

          The only problem is that I have no clue how you got it

          :o
          - There's no replacement for displacement.

          "It's not peer pressure, it's just your turn."

          AO Teenage Mutant Ninja Turtle: Donatello

            Comment

            • pbguy888
              Registered User
              • Jun 2002
              • 1215
              #4
              i got -2...
              -AKA Viking
              -WASED Out
              -Halo B,rip drive,z code
              -14 in. Ultralite

                Comment

                • Miscue
                  Super Moderator

                  • Oct 2000
                  • 7105
                  #5
                  (x - 1)
                  -------
                  (x + 2)


                  (1/x - 1)
                  ---------
                  (1/x + 2)

                  (1/x - 1) &nbsp&nbsp&nbsp&nbsp x
                  --------- x ----
                  (1/x + 2) &nbsp&nbsp&nbsp&nbsp x

                  (1 - x)
                  --------
                  (1 + 2x)

                    Comment

                    • 71 LS6
                      Nick Tahou's guru
                      • May 2002
                      • 230
                      #6


                      Thanks again miscue, now I see what i did wrong (stupid careless idiot mistake). That helps a lot, now I can go to bed
                      - There's no replacement for displacement.

                      "It's not peer pressure, it's just your turn."

                      AO Teenage Mutant Ninja Turtle: Donatello

                        Comment

                        • Miscue
                          Super Moderator

                          • Oct 2000
                          • 7105
                          #7
                          Alright, I helped you with yours... your turn to help me with mine:

                          Suppose that g(x) and g'(x) are continuous on (a,b) and that |g'(x)| > 1 on this interval. If the fixed point P and the initial approximations p0 and p1 lie in the interval (a,b), then show that p1 = g(p0) implies that |E1| = |P - p1| > |P - p0| = |E0|

                          This stuff gives me a headache just reading it.

                            Comment

                            • 71 LS6
                              Nick Tahou's guru
                              • May 2002
                              • 230
                              #8
                              I really wish I could help you with that, but I'm completely lost on that question. In fact, I don't even know where to begin. Sorry

                              BTW, what math course are you in?
                              - There's no replacement for displacement.

                              "It's not peer pressure, it's just your turn."

                              AO Teenage Mutant Ninja Turtle: Donatello

                                Comment

                                • rhetor22
                                  Mag Lover (not that way)
                                  • Nov 2001
                                  • 1207
                                  #9
                                  it makes me conserned that before summer started i could easily do one of those equations, but now, i have no idea where to begin.


                                  My truck is louder than yours. A lot louder.

                                  Good Traders: JT2002, LawFox32, Gizmolax32

                                    Comment

                                    • -Jôker-
                                      AOs Original JoKeR
                                      • Nov 2000
                                      • 2132
                                      #10
                                      i have triuble in algebra!!! this is WAAAAAAYYYYY over my head lol glad we have bsome brains here

                                        Comment

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