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Quadratic Functions

  1. Nov 17, 2003 #1
    2 questions

    1.can a quadratic function be just set to 1 number e.g. 5 or can it be a bigger number. at the moment im working on numbers below 10 to get used to the formulas.

    2. is this correct how i am doing it?


    N --> N2--> 3N2 + 4


    N =5

    5 x 5 = 25 = N2

    5 x 25 = 75 = 3N2

    N = 79 answer

    is that correct?
  2. jcsd
  3. Nov 17, 2003 #2


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    Science Advisor

    Your questions are awkwardly written but I think what you want is:

    given y= ax2+ bx+ c, you can choose x to be any number you want, then calculate y.

    In particular, if y= 3N2+ 4, you would, just as you say, first, find N2, then multiply by 3, then add 4.
  4. Nov 17, 2003 #3
    thats it, yea im still practicing the equations. i thought Y2 were that if you had Y = 5 then Y2. Then to find Y2 we multiply the 5 by in this case Y2 to get 25 as Y2 would be 25 then mutliply 3N2 by the 25 to get 75 + 4 to get 79

    is that ok?:smile:
  5. Nov 18, 2003 #4


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    I'm assuming that English is not your native language so I won't be quite as harsh as I could be!

    Much of this makes no since at all: "i thought Y2 were that if you had Y = 5 then Y2." Then what?? I assume you meant to write "then Y2= 52".

    But you also write "Then to find Y2 we multiply the 5 by in this case Y2". No, you multiply 5 by itself- that's what "2" means.

    "then mutliply 3N2 by the 25". No, "N2" is 25. You only multiply the 3 by 25. By the way, it's a really, really bad idea to suddenly switch from "Y" to "N".

    To calculate 3N2+ 4, for N= 5, you replace the N by 5:
    3(5)2+ 4= 3(25)+ 4= 75+ 4= 79.
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