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    X^4-8X^2+8 how do i solve this with a caculator btw i havnt got the grey one. or can i use the quadratin formula??
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    x^4 - 8x^2 + 8=0
    Yeah if you let y=x^2
    then you get
    y^2 - 8y + 8=0

    And you use the quadratic formula to find y.

    When you've found it, square root it to find x, because x=\sqrt yand make sure to take both the positive and negative square root. i.e. \sqrt4=\pm2
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    (Original post by maxfire)
    i.e. \sqrt4=\pm2
    I should point out that this isn't actually correct. \sqrt{4} = 2 unambiguously (only +2, not -2), however the solutions to the equation a^2 = 4 are given by a = \pm \sqrt{4} = \pm 2 (the square root always refers to the positive root).

    Other than that, what maxfire said is right. That is, you should take the positive and negative square roots.
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    (Original post by maxfire)
    x^4 - 8x^2 + 8=0
    Yeah if you let y=x^2
    then you get
    y^2 - 8y + 8=0

    And you use the quadratic formula to find y.

    When you've found it, square root it to find x, because x=\sqrt yand make sure to take both the positive and negative square root. i.e. \sqrt4=\pm2
    thank youuu
 
 
 
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Updated: January 18, 2010
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