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Math Help - algebra

  1. #1
    abc
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    algebra

    To sove a economic question i need to use algebra first.

    P= - 1/4Qd+6.75

    P = 1/2Qs + 2



    So i got for the first step:

    1/4 Qd = - p + 48

    1/2 Qs = p - 2

    but i need to get the 1/4 and 1/2 on the right side which i don't know how.

    I would reall appreciate your help.
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  2. #2
    Bar0n janvdl's Avatar
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    Quote Originally Posted by abc View Post
    To sove a economic question i need to use algebra first.

    P= - 1/4Qd+6.75

    P = 1/2Qs + 2



    So i got for the first step:

    1/4 Qd = - p + 48

    1/2 Qs = p - 2

    but i need to get the 1/4 and 1/2 on the right side which i don't know how.

    I would reall appreciate your help.
     - \frac{1}{4} Qd + 6,75 = \frac{1}{2} Qs + 2

    (Multiply by 4 straight through)

    -Qd + 27 = 2Qs + 8

    2Qs + Qd = 21

    Can you take over from here?

    EDIT: Hint: Isolate Qd and set it back into the first equation
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  3. #3
    abc
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    Quote Originally Posted by janvdl View Post
     - \frac{1}{4} Qd + 6,75 = \frac{1}{2} Qs + 2

    (Multiply by 4 straight through)

    -Qd + 27 = 2Qs + 8

    2Qs + Qd = 21

    Can you take over from here?

    EDIT: Hint: Isolate Qd and set it back into the first equation
    It think you have used it as one formula but they are seperate so i need to get 1/4 in the first formula to the right side so it is in the format of Qd=.... the same applies to the 1/2Qs one. So in the end i will have two answers. One being Qd equals and one Qs equals.
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  4. #4
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    1/2 Qs = p - 2
    Good so far. Now divide both sides of the equals sign by 1/2.

    \frac {1/2 Qs}{1/2} = \frac {p-2}{1/2}
    Qs = 2(p-2)
    Qs = 2p-4

    P= - 1/4Qd+6.75
    Add 1/4Qd to both sides:
    P+1/4Qd = -1/4Qd+6.75+1/4Qd
    P+1/4Qd = 6.75

    Now subtract P from both sides
    P+1/4Qd-P = 6.75-P
    1/4Qd = 6.75 -P

    Then divide both sides by 1/4
    <br />
\frac {1/4Qd}{1/4} = \frac {6.75-p}{1/4}
    Qd = 4(6.75 - p)
    Qd = 27-4p
    Last edited by badgerigar; January 8th 2008 at 05:04 PM. Reason: cleaned up latex
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