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Math Help - Rational Roots

  1. #1
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    Rational Roots

    Just quick:

    I have (2x^4)+(4x^3)-(5x^2)-5x+2.
    The only possible rational roots by the Rational Root Test are 1,-1,2,-2,.5,-.5.
    The only one that works out of these is -1. Could someone just check this for me?

    Jimmy
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  2. #2
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    Quote Originally Posted by JimmyT View Post
    Just quick:

    I have (2x^4)+(4x^3)-(5x^2)-5x+2.
    The only possible rational roots by the Rational Root Test are 1,-1,2,-2,.5,-.5.
    The only one that works out of these is -1. Could someone just check this for me?

    Jimmy
    I agree. Good work!

    You can always check these by division as well. You should be able to divide 2x^4+4x^3-5x^2-5x+2 by x - (-1) either by long or synthetic division to find:
    2x^4+4x^3-5x^2-5x+2 = (x+1)(2x^3+2x^2-7x+2)
    confirming that there is no remainder.

    -Dan
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