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Homework Help: Similtanious equation help?

  1. May 1, 2010 #1
    Just doing a bit of math homework and im stuck on 2 questions

    the first one is a similtanoius equation and goes like this

    y = x - 1
    y = x2 -3

    ive been trying for about half an hour and all i end up with is

    y = (square root of) y - 2

    im not sure if it's right, it does not look it.

    the 2nd question i dont know the name of and looks like

    72x = 49

    i dont even know where to begin on that, i just have to factorise it.

    thankyou in advanced
     
  2. jcsd
  3. May 1, 2010 #2

    rock.freak667

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    Instead of substituting for x, substitute for y instead.


    Can you write 49 in any way that relates to 7?
     
  4. May 1, 2010 #3
    for the 2nd question i know that x = 1 but i dont know how to write the proof, like in another question how would i do

    43-x = 8x

    1st question solved thankyou rock.freak667
     
    Last edited: May 1, 2010
  5. May 1, 2010 #4

    rock.freak667

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    It all revolves around how you can write the base numbers. If you have am=an then m=n.

    So if you have 36=62x, then you can write this as 62=62x which means that 2=2x and hence x=1.
     
  6. May 1, 2010 #5

    Also remember how a power to a power behaves:
    [tex](a^b)^c = a^{bc}[/tex]

    so:
    [tex](8)^x=(2^3)^x=2^{3x}[/tex]

    and

    [tex](4)^{3-x}=(2^2)^{3-x}=2^{6-2x}[/tex]

    edit: I misread and thought you said this problem's solution was x = 1. My bad!
     
  7. May 1, 2010 #6

    rock.freak667

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    Right so now you have

    [tex]2^{6-2x}=2^{3x}[/tex]

    so what is x?
     
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