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Math Help - Something wrong with my working.

  1. #1
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    Something wrong with my working.

    Hi guys,

    Have answered this question, but when I checked the final answer it should be 7 not 11. Can you help me with where I went wrong. Cheers.

    (a) Expand ( x + ⅟x ) = x + 2x⅟x + ⅟x₂
    = x + 2 + ⅟x₂

    (b) Suppose that x + ⅟x = 3. Use part (a) to evaluate x + ⅟x without attempting to find the value of x.
    ( x + ⅟x ) = x + 2 + ⅟x₂
    If x + ⅟x = 3, then = ( x + ⅟x )
    = ( 3 )
    = 9
    Thus x + 2 + ⅟x₂ = x + ⅟x₂ + 2
    = 9 + 2
    So x + ⅟x₂ = 11
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  2. #2
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    Hello my friend

    Quote Originally Posted by Joel View Post
    Hi guys,

    Have answered this question, but when I checked the final answer it should be 7 not 11. Can you help me with where I went wrong. Cheers.

    (a) Expand ( x + ⅟x ) = x + 2x⅟x + ⅟x₂
    = x + 2 + ⅟x₂
    This is correct!

    Quote Originally Posted by Joel View Post
    (b) Suppose that x + ⅟x = 3. Use part (a) to evaluate x + ⅟x without attempting to find the value of x.
    ( x + ⅟x ) = x + 2 + ⅟x₂
    If x + ⅟x = 3, then = ( x + ⅟x )
    = ( 3 )
    = 9
    Thus x + 2 + ⅟x₂ = x + ⅟x₂ + 2
    = 9 + 2
    So x + ⅟x₂ = 11
    No, Thus x^2+2 + \frac{1}{x^2} = 9
    So

    x^2+\frac{1}{x^2} = 9 - 2
    Hence

    x^2+\frac{1}{x^2} = 7

    Yours
    Rapha
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  3. #3
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    If x + ⅟x = 3

    ( x + ⅟x ) = (3)

    From (a)

    x + 2 + ⅟x₂ = (3)
    x + 2 + ⅟x₂ = 9

    Subtract 2 from both sides

    x + ⅟x₂ = 7

    Is that your working ???
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  4. #4
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    Yes, it is
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