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Math Help - need to solve for x

  1. #1
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    need to solve for x

    1.67*10^{-9}=.01x+.4x^2+4x^3
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  2. #2
    Senior Member Stroodle's Avatar
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    Using a calc, the answer is:

    x\approx 1.670 \times 10^{-7}

    I don't think you can solve this one by hand...
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  3. #3
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    What did you type into the calculator to get that answer? I guess I should have said that I already knew the answer since it was in the back of the book but I have no idea how to get the answer.
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  4. #4
    Senior Member Stroodle's Avatar
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    I have a CAS calculator (Casspad 330), so I just typed in the equation to solve.

    You can also go here Wolfram|Alpha and type in:

    solve 1.67*10^{-9}=0.01x+0.4x^2+4x^3
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  5. #5
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    Quote Originally Posted by Stroodle View Post
    I have a CAS calculator (Casspad 330), so I just typed in the equation to solve.

    You can also go here Wolfram|Alpha and type in:

    solve 1.67*10^{-9}=0.01x+0.4x^2+4x^3
    okay thanks but I doubt they would put a problem in a book that you couldnt solve with at least a basic ti-XX graphing calculator. There has to be some way to do it on paper.
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  6. #6
    Senior Member Stroodle's Avatar
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    Yeah, I'm sure you can do it with a TI too. Unfortunately I can't remember how to use one... Have you tried plotting the graph on it?

    I really don't know how you would find the solution without a calc - without a stupendous amount of trial and error..
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