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Math Help - Intervals

  1. #1
    Newbie
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    Sep 2009
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    Intervals

    Given the function f(x)= -2x^3+x+6, find an interval of length one(for example (3,4) or (-1,0) or (-5,-4)) on the x-axis where there is guranteed to be a zero. Explain your answer.

    Thank you!
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  2. #2
    MHF Contributor
    Joined
    Mar 2007
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    1,240

    Talking

    Find some x-value where the value of y is negative. Find some other x-value where the value of y is positive. Pick x-values between these two, until you have x-values one unit apart, where one x-value gives a negative y-value and the other gives a positive y-value.

    Zero has to be between negative and positive.
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