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    The strange thing is that I would start by equating the two discriminants, but the answer has the power three in it, so how?

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    (Original post by Gmart)
    The strange thing is that I would start by equating the two discriminants, but the answer has the power three in it, so how?

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    q^2-8pr=0 so r=\frac{q^2}{8p}

    Subbing that into p^2-4r(-q+1)=0 gives you the cube of q.


    EDIT: I think saying q^2-8pr=p^2-4r(-q+1) is a common mistake which some might do given the wording
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    (Original post by RDKGames)
    q^2-8pr=0 so r=\frac{q^2}{8p}

    Subbing that into p^2-4r(-q+1)=0 gives you the cube of q.


    EDIT: I think saying q^2-8pr=p^2-4r(-q+1) is a common mistake which some might do given the wording
    Thanks - indeed I did!! Whoops!
 
 
 
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