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Math Help - What am I doing wrongly?

  1. #1
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    What am I doing wrongly?

    I have the following equation:

    36x^(4)-126^(2)+108=0

    The solutions are -1.41, 1.41, -1.22, 1.22 I was attempting to expedite the process of plugging in these numbers to said equation, so I put the above equation in y1 exactly as I typed it (except, of course, without the = 0.) Then I went to the homescreen and hit vars-yvars-function-y1 then i put (1.22, etc.) to test the points. None of them equalled zero... I am using TI 83 plus. Thanks for the help.
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  2. #2
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    Re: What am I doing wrongly?

    Quote Originally Posted by benny92000 View Post
    I have the following equation:

    36x^(4)-126^(2)+108=0

    The solutions are -1.41, 1.41, -1.22, 1.22 I was attempting to expedite the process of plugging in these numbers to said equation, so I put the above equation in y1 exactly as I typed it (except, of course, without the = 0.) Then I went to the homescreen and hit vars-yvars-function-y1 then i put (1.22, etc.) to test the points. None of them equalled zero... I am using TI 83 plus. Thanks for the help.
    I assume you mean ...

    y = 36x^4 - 126x^2 + 108

    18(2x^2 - 3)(x^2 - 2) = 0

    x = \pm \sqrt{2}

    x = \pm \sqrt{\frac{3}{2}}

    if you're using those rounded solutions in Y1, the calculator will not give you back 0. my advice is store the unrounded solutions into a alpha register and try evaluating the stored value.
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  3. #3
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    Re: What am I doing wrongly?

    Great, thanks!
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