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Math Help - someone help!

  1. #1
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    someone help!

    The equation 2k - 4k^(3/2) + 1 = 0
    Subsitute p for k to find the value of k.

    i got 2p-4p + 1, and it doesnt factorise to give k=0.44, which is at the back of the book!

    i even used the discriminant thing.
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  2. #2
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    earboth's Avatar
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    Quote Originally Posted by ify00
    The equation 2k - 4k^(3/2) + 1 = 0
    Subsitute p for k to find the value of k.
    i got 2p-4p + 1, and it doesnt factorise to give k=0.44, which is at the back of the book!
    i even used the discriminant thing.
    Hello,

    keep in mind:

    p^2=k^3 \Longrightarrow k=\sqrt[3]{p^2}

    2p^2-4p+1=0\Longleftrightarrow p=1+{1\over2}\sqrt{2}\ \vee  \ p=1-{1\over2}\sqrt{2}

    Now plug in these values of p into the equation to calculate k and you'll get:

    k=\sqrt[3]{\left( 1+{1\over2}\sqrt{2} \right)^2} \approx 1.4283... or

    k=\sqrt[3]{\left( 1-{1\over2}\sqrt{2} \right)^2} \approx .4410...

    Greetings

    EB
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