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Math Help - Can someone help me with this pre-Calculus question?

  1. #1
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    Can someone help me with this pre-Calculus question?

    If 2x^2-dx+(31-d^2)x+5 has a factor of x - d, what is the value of d if d is an integer?
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  2. #2
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    Re: Can someone help me with this pre-Calculus question?

    Hint: f(d)=2(d)^2-d(d)+(31-d^2)(d)+5=2d^2-d^2+31d-d^2+5=0

    Write in standard form:

    d^3-d^2-31d-5=0

    Now, use the rational roots theorem to see if this cubic has any integral roots.
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  3. #3
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    Re: Can someone help me with this pre-Calculus question?

    Small missing step: If x-a is a factor of a polynomial P(x), then P(a) = 0 (Remainder theorem).

    Salahuddin
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  4. #4
    MHF Contributor MarkFL's Avatar
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    Re: Can someone help me with this pre-Calculus question?

    That missing step was given in a duplicate post in another forum. I didn't feel it necessary to repeat it, but rather continued the discussion here after he was asked to post in an appropriate forum.
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