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    Please show me how to solve this without a calculator!
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    (Original post by Phoenix Everill)
    Please show me how to solve this without a calculator!
    Multiply both sides by x^2 and solve. Please post your working if you need any further hints.
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    (Original post by RogerOxon)
    Multiply both sides by x^2 and solve. Please post your working if you need any further hints.
    (Original post by Phoenix Everill)
    Please show me how to solve this without a calculator!
    just put the second term into terms of x^(-2), using the 4.
    then solve
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    (Original post by ThatsAGoodOne349)
    just put the second term into terms of x^(-2), using the 4.
    then solve
    Thank you for your reply
    so:

    x^4 + 4 = 12x^2
    => x^4 + 4 - 12 = 0
    => x^2 + 4x^(-2) -12 = 0

    Then I don't know how to solve, sorry.
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    (Original post by Phoenix Everill)
    Thank you for your reply
    so:

    x^4 + 4 = 12x^2
    => x^4 + 4 - 12 = 0
    => x^2 + 4x^(-2) -12 = 0

    Then I don't know how to solve, sorry.
    you got that right
    Google time
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    (Original post by Phoenix Everill)
    Thank you for your reply
    so:

    x^4 + 4 = 12x^2
    => x^4 + 4 - 12 = 0
    => x^2 + 4x^(-2) -12 = 0

    Then I don't know how to solve, sorry.
    x^2+\frac{4}{x^2}=12

    \therefore x^4-12x^2+4=0 (we need to ignore x=0, if it were a solution)

    Now solve it as a quadratic in x^2.
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    (Original post by Phoenix Everill)
    Thank you for your reply
    so:

    x^4 + 4 = 12x^2
    => x^4 + 4 - 12 = 0
    => x^2 + 4x^(-2) -12 = 0

    Then I don't know how to solve, sorry.
    (Original post by ThatsAGoodOne349)
    you got that right
    Nope - the intermediate step is wrong. What happened to the 12x^2 in the second line?
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    (Original post by RogerOxon)
    Nope. What happened to the 12x^2?
    nono
    you got rid of the fraction

    try using the x^4 +4 = 12x^2 and using this:
    y =x^2
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    (Original post by Phoenix Everill)
    Thank you for your reply
    so:

    x^4 + 4 = 12x^2
    => x^4 + 4 - 12 = 0
    => x^2 + 4x^(-2) -12 = 0

    Then I don't know how to solve, sorry.
    (Original post by ThatsAGoodOne349)
    you got that right
    Google time
    They didn't - the bold line is wrong.

    (Original post by RogerOxon)
    x^2+\frac{4}{x^2}=12

    \therefore x^4-12x^2+4=0 (we need to ignore x=0, if it were a solution)

    Now solve it as a quadratic in x^2.
    (Original post by ThatsAGoodOne349)
    nono
    you got rid of the fraction
    Why do you think that's a problem?
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    (Original post by RogerOxon)
    Why do you think that's a problem?
    My last post...
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    (Original post by ThatsAGoodOne349)
    My last post...
    You must have misread what I posted. We're in violent agreement.
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    (Original post by RogerOxon)
    You must have misread what I posted. We're in violent agreement.
    LOL
    okay
    let's go with the substitution thing
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    RogerOxon
    you didn't mention substitution inn that post
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    (Original post by ThatsAGoodOne349)
    RogerOxon
    you didn't mention substitution inn that post
    What substitution?
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    (Original post by RogerOxon)
    What substitution?
    y=x^2
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