Algebraic Fractions

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  1. zed963's Avatar
    1 16-07-2012  20:13
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    Algebraic Fractions
    Solve this quadratic equation.

    Name: 17.gif Views: 162 Size: 338 Bytes

    Should I move the left hand side to the right or shall I just leave it as it is and just cross multiply?
  2. Plato's Trousers's Avatar
    2 16-07-2012  20:16
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    Re: Algebraic Fractions
    (Original post by zed963)
    Solve this quadratic equation.

    Name: 17.gif Views: 162 Size: 338 Bytes

    Should I move the left hand side to the right or shall I just leave it as it is and just cross multiply?
    The clue's in the question - solve this quadratic equation. Cross multiply then solve. Post what you get
    Last edited by Plato's Trousers; 16-07-2012 at 20:21.
  3. zed963's Avatar
    3 16-07-2012  20:23
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    Re: Algebraic Fractions
    [QUOTE=Plato's Trousers;38582635]The clue's in the question - solve this quadratic equati


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  4. zed963's Avatar
    4 16-07-2012  20:24
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    Re: Algebraic Fractions
    (Original post by Plato's Trousers)
    The clue's in the question - solve this quadratic equation. Cross multiply then solve. Post what you get
    Could you not do 5x-1/3 - 6/x =0
  5. Plato's Trousers's Avatar
    5 16-07-2012  20:25
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    Re: Algebraic Fractions
    [QUOTE=zed963;38582714]
    (Original post by Plato's Trousers)
    The clue's in the question - solve this quadratic equati


    Click image for larger version.  Name: 17.gif  Views: 41  Size: 999 Bytes  ID: 163300
    nope.

    18=5x^2 - x

    5x^2-x-18=0
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  6. zed963's Avatar
    6 16-07-2012  20:27
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    Re: Algebraic Fractions
    [QUOTE=Plato's Trousers;38582748]
    (Original post by zed963)

    nope.

    18=5x^2 - x

    5x^2-x-18=0
    Why don't we move the 3x onto the right hand side?
  7. Plato's Trousers's Avatar
    7 16-07-2012  20:29
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    Re: Algebraic Fractions
    [QUOTE=zed963;38582775]
    (Original post by Plato's Trousers)

    Why don't we move the 3x onto the right hand side?
    what 3x?

    You are cross multiplying. So LHS bottom times RHS top and vice versa

    3 \times 6 = x(5x-1)

    18=5x^2 - x

    ok?
  8. zed963's Avatar
    8 16-07-2012  20:34
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    Re: Algebraic Fractions
    [QUOTE=Plato's Trousers;38582801]
    (Original post by zed963)

    what 3x?

    You are cross multiplying. So LHS bottom times RHS top and vice versa

    3 \times 6 = x(5x-1)

    18=5x^2 - x

    ok?
    But the denominator is 3x so don't we move it to the right hand side.

    I'm looking at this website tbh and thats what its telling me to do.

    http://www.revisesmart.co.uk/maths/c...fractions.html
  9. Plato's Trousers's Avatar
    9 16-07-2012  20:36
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    Re: Algebraic Fractions
    [QUOTE=zed963;38582846]
    (Original post by Plato's Trousers)

    But the denominator is 3x so don't we move it to the right hand side.

    I'm looking at this website tbh and thats what its telling me to do.

    http://www.revisesmart.co.uk/maths/c...fractions.html
    eh? That's not the question you posted. there is no 3x term in the question you posted.

    this was your question

    \dfrac{6}{x}=\dfrac{5x-1}{3}

    right?
    Last edited by Plato's Trousers; 16-07-2012 at 20:38.
  10. zed963's Avatar
    10 16-07-2012  20:38
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    Re: Algebraic Fractions
    [QUOTE=Plato's Trousers;38582883]
    (Original post by zed963)

    eh? That's not the question you posted.
    I know it isn't but its an example that I've been following, what method would you use then?

    and what you do with the lowest common denominator in the fraction?
  11. zed963's Avatar
    11 16-07-2012  20:40
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    Re: Algebraic Fractions
    [QUOTE=Plato's Trousers;38582883]
    (Original post by zed963)

    eh? That's not the question you posted. there is no 3x term in the question you posted.

    this was your question

    \dfrac{6}{x}=\dfrac{5x-1}{3}

    right?

    Yes that was the question
  12. TenOfThem's Avatar
    12 16-07-2012  20:41
    • TSR Royalty
    Re: Algebraic Fractions
    \frac{6}{x} = \frac{5x-1}{3}

    You started off ok

    \frac{(6)(3x)}{x} = \frac{(5x-1)(3x)}{3}

    But then

    (6)(3) = (5x-1)(x)

    and

    18=5x^2-x
  13. pseudonymegg's Avatar
    13 16-07-2012  20:42
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    Re: Algebraic Fractions
    X = -9 or +2
  14. Plato's Trousers's Avatar
    14 16-07-2012  20:42
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    Re: Algebraic Fractions
    [QUOTE=zed963;38582913]
    (Original post by Plato's Trousers)

    I know it isn't but its an example that I've been following, what method would you use then?

    and what you do with the lowest common denominator in the fraction?
    you cross multiply as I have shown you. If you want to do it another way you can subtract the fractions,

    \dfrac{18-x(5x-1)}{3x}=0

    \dfrac{18-5x^2+x}{3x}=0

    but the first way is easier
    Last edited by Plato's Trousers; 16-07-2012 at 20:43.
  15. zed963's Avatar
    15 16-07-2012  20:42
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    Re: Algebraic Fractions
    (Original post by TenOfThem)
    \frac{6}{x} = \frac{5x-1}{3}

    You started off ok

    \frac{(6)(3x)}{x} = \frac{(5x-1)(3x)}{3}

    But then

    (6)(3) = (5x-1)(x)

    and

    18=5x^2-x
    Oh right so in these type of questions you don't take the denominator to the right hand side then, you just cancel it off.
  16. Plato's Trousers's Avatar
    16 16-07-2012  20:46
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    Re: Algebraic Fractions
    (Original post by pseudonymegg)
    X = -9 or +2
    nope

    x=-9/5 or 2
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  17. TenOfThem's Avatar
    17 16-07-2012  20:46
    • TSR Royalty
    Re: Algebraic Fractions
    (Original post by zed963)
    Oh right so in these type of questions you don't take the denominator to the right hand side then, you just cancel it off.
    I did multiply the RHS by 3x ... did you not see that?
  18. pseudonymegg's Avatar
    18 16-07-2012  20:47
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    Re: Algebraic Fractions
    6/x = 5x-1/3

    6(3) = x(5x-1)

    18= 5x"2-x (-18)

    0 = 5x"2-x-18

    (5x+9) (x-2) = 0

    x= -1.8 or 2
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    1
  19. pseudonymegg's Avatar
    19 16-07-2012  20:48
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    Re: Algebraic Fractions
    (Original post by Plato's Trousers)
    nope

    x=-9/5 or 2
    whoops i'm a bit rusty sorry I just re-posted the correct answer
  20. TenOfThem's Avatar
    20 16-07-2012  20:48
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    Re: Algebraic Fractions
    (Original post by zed963)
    Oh right so in these type of questions you don't take the denominator to the right hand side then, you just cancel it off.
    There is no "these types of questions"

    the method is the same for all

    multiply all elements by the common denominator ... then cancel appropriately





    there are short cuts if you start to feel confident
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