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    mathshelp Posts: 3, Reputation: 1
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    #1

    Apr 29, 2009, 07:26 AM
    Rearranging Formula
    I have two questions that I am having trouble with, I don't so much want the answers but the method of how to work them out:

    Transpose these equations to make the 'y' the subject.

    (1) 7(6-3y) + 5(2y+4) = 4x+9

    (2) 4x/3 +1 = 3y/2 - 6


    Were ' / ' means divide.
    Perito's Avatar
    Perito Posts: 3,139, Reputation: 150
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    #2

    Apr 29, 2009, 07:33 AM

    1.
    a. Multiply out the expressions, 7(6-3y) and 5(2y+4).
    b. collect like terms (add/subtract constants, add coefficients of y
    c. Subtract the constant from both sides.
    c. Solve the equation for y by dividing by the coefficient of y.

    2.
    a. multiply both sides of the equation by 6 (to get rid of the denominators).
    b. Add a constant (36) to both sides of the equation.
    c. Divide both sides of the equation by the coefficient of y. That will solve for y in terms of x
    (I think that's what it means to make "y" the subject, but we never used that terminology when I was in school).
    mathshelp's Avatar
    mathshelp Posts: 3, Reputation: 1
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    #3

    Apr 29, 2009, 07:49 AM
    Quote Originally Posted by Perito View Post
    1.
    a. Multiply out the expressions, 7(6-3y) and 5(2y+4).
    b. collect like terms (add/subtract constants, add coefficients of y
    c. Subtract the constant from both sides.
    c. Solve the equation for y by dividing by the coefficient of y.

    2.
    a. multiply both sides of the equation by 6 (to get rid of the denominators).
    b. Add a constant (36) to both sides of the equation.
    c. Divide both sides of the equation by the coefficient of y. That will solve for y in terms of x
    (I think that's what it means to make "y" the subject, but we never used that terminology when I was in school).

    Thanks for your help.
    I have worked them out, please could you confirm if there right:

    1.
    42 - 21y + 10y + 20 = 4x + 9
    42 + 20 - 21y + 10y
    62 - 11y = 4x + 9
    -11y = 4x + 9 - 62 (x -1)
    11y = -4x + 53

    y= 4x+53 /11

    2.
    24x/18 + 6 = 18y/12 - 36
    24x/18 + 42 = 18y/12
    24x + 42 = y/12
    y/12 = 24x + 42
    y = 24x+42/12
    Perito's Avatar
    Perito Posts: 3,139, Reputation: 150
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    #4

    Apr 29, 2009, 08:00 AM
    Quote Originally Posted by mathshelp View Post
    Thanks for your help.

    1.
    42 - 21y + 10y + 20 = 4x + 9
    42 + 20 - 21y + 10y
    62 - 11y = 4x + 9
    -11y = 4x + 9 - 62 (x -1) <-- not sure where that came from but you didn't carry it through so it's ok.
    11y = -4x + 53

    y= 4x+53 /11
    1 is OK. 2 needs some work.



    multiply by 6







    You can take it from there.
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    mathshelp Posts: 3, Reputation: 1
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    #5

    Apr 29, 2009, 08:11 AM
    Quote Originally Posted by perito View Post
    1 is ok. 2 needs some work.



    multiply by 6







    you can take it from there.
    thank you

    this has helped me a lot.

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