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Math Help - Finding formula for a function

  1. #1
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    Finding formula for a function

    I need to find the formula for this function, and i'm not sure what to do...

    Code:
    x     f(x)
    -2    -25.22
    0      3.50
    2      32.22
    4      60.94
    6      89.66
    I've looked all over the internet and can't find anything to help me out
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  2. #2
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by JAMESveeder View Post
    I need to find the formula for this function, and i'm not sure what to do...

    Code:
    x     f(x)
    -2    -25.22
    0      3.50
    2      32.22
    4      60.94
    6      89.66
    I've looked all over the internet and can't find anything to help me out
    We can model the function using a linear equation.

    Note that when x increases by 2, f(x) increases by 28.72

    Since f(0)=3.5=b and the slope of the line is m=\frac{28.72}{2}=14.36, it follows that the equation of the line is f(x)=mx+b=14.36x+3.50.
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  3. #3
    Grand Panjandrum
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    Quote Originally Posted by JAMESveeder View Post
    I need to find the formula for this function, and i'm not sure what to do...

    Code:
    x     f(x)
    -2    -25.22
    0      3.50
    2      32.22
    4      60.94
    6      89.66
    I've looked all over the internet and can't find anything to help me out
    Try plotting it!

    It's a straight line passing through (0,3.5) and with slope 14.36

    CB
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  4. #4
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    Great explanation, thank you!

    You can't use the same method for an exponential function though, can you?
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  5. #5
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    Quote Originally Posted by JAMESveeder View Post
    Great explanation, thank you!

    You can't use the same method for an exponential function though, can you?
    No. For an exponential function, you would need to find a common RATIO. In other words, you need to find what each number is MULTIPLIED by to get the next.
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  6. #6
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    So with this:
    Code:
    x      g(x)
    .5     -1
    1       0
    2       1
    4       1
    8       3
    Each number is multiplied by 2

    So how would I apply that to the explanation that was said before?
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  7. #7
    Grand Panjandrum
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    Quote Originally Posted by JAMESveeder View Post
    So with this:
    Code:
    x      g(x)
    .5     -1
    1       0
    2       1
    4       2
    8       3
    Each number is multiplied by 2

    So how would I apply that to the explanation that was said before?
    you would find the line through the data: x,\ \log_2(g(x)) .. or on second thoughts \log_2(x),\ g(x)

    CB
    Last edited by CaptainBlack; August 25th 2009 at 02:27 AM.
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  8. #8
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    Ah, thanks CaptainBlack

    This helps a lot, thanks very much guys.
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