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Math Help - Algebra and Surds!

  1. #1
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    Algebra and Surds!

    Find the exact value of

    x + 1/x

    if x = 1 + 2 * square root of 3 / 1 - 2 * square root of 3

    Answer: 434/121 = 3 71/121
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  2. #2
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    Does anyone end up with this answer?? Pls help! I dnt kno whether it's a printing error in the textbook or I just cnt solve it
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  3. #3
    MHF Contributor Also sprach Zarathustra's Avatar
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    Quote Originally Posted by Mirage View Post
    Does anyone end up with this answer?? Pls help! I dnt kno whether it's a printing error in the textbook or I just cnt solve it
    Answer: 434/121 = 3 71/121
    Your answer is correct!
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  4. #4
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    Thanks for your response

    I don't know how to arrive at that answer. Would you be able to type out your working out pls?
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  5. #5
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    Would be more helpful if you used some brackets, is this the question? find \frac{x^2+1}{x^2} where x = \frac{1+2\sqrt{3}}{1-2\sqrt{3}}
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  6. #6
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    It is x + (1/x)
    second part is correct

    Sorry, I'm new to this. How do you type maths? Is there some sort of program that you use?
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  7. #7
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    Quote Originally Posted by Mirage View Post

    Sorry, I'm new to this. How do you type maths? Is there some sort of program that you use?
    Have a quick read of this. http://www.mathhelpforum.com/math-he...orial-266.html
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  8. #8
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    Quote Originally Posted by Mirage View Post
    It is x + (1/x)
    (\frac{1+2\sqrt{3}}{1-2\sqrt{3}})^2+\frac{1}{(\frac{1+2\sqrt{3}}{1-2\sqrt{3}})^2}

    Start expanding brackets.
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  9. #9
    MHF Contributor Also sprach Zarathustra's Avatar
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    You also can find x+1/x=2cos(t) (much easier )

    and then x^2+(1/x^2)=2cos(2t)
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  10. #10
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    Quote Originally Posted by Also sprach Zarathustra View Post
    You also can find x+1/x=2cos(t) (much easier )

    and then x^2+(1/x^2)=2cos(2t)
    Good advice ASZ, although remember this is in a pre-uni level forum.
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