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Thread: roots q

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    roots q

    so I have the equation 2x^3 +3x^2 +x -5=0

    when I sub in x=1/square root (y) then the answer should be 25y^3 -31y^2 +5y -4=0 but I cant seem to get that

    also when I sub in x=root y, I should get 4y^3 -5y^2 +31y -25=0 but how

    thank u

  2. #2
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    Re: roots q

    If you try to manipulate using index laws, this becomes easier.





    Multiply by to remove negative indices:



    Shuffle terms around:



    Square both sides to remove fractional indices:



    Clearly , so divide by :



    Shuffle terms again:

    Last edited by fan96; 9 Feb 2018 at 7:41 PM.
    sssona09 likes this.
    HSC 2018 - [English Adv.] • [Maths Ext. 1] • [Maths Ext. 2] • [Chemistry] • [Software Design and Development]

    1(3√3) t2 dt cos(3π/9) = log(3√e) | Integral t2 dt, From 1 to the cube root of 3. Times the cosine, of three pi over nine, Equals log of the cube root of e.

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    Re: roots q

    thank you so much!!!

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