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Math Help - real roots

  1. #1
    Senior Member furor celtica's Avatar
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    real roots

    ok so there's curve y=12x+3(x^2)-2(x^3)
    the stationary points are (-1,-7) and (2,20)
    i'm supposed to find the domain for which y has three real roots
    the answer is -20<x<7, this is a typo right?
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  2. #2
    A Plied Mathematician
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    The answer -20<x<7 appears to correspond, possibly, to the question "What is the range for y corresponding to the domain that includes three real roots?" Then the answer given would be correct.
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  3. #3
    Senior Member furor celtica's Avatar
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    oh sorry my mistake i meant that, but wouldnt the answer be -7<y<20?
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  4. #4
    A Plied Mathematician
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    Oh, yeah. That's correct. It should be -7<y<20. I didn't know to what you were objecting, so I didn't look closely at the actual numbers.
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