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Math Help - Changing the subject involving division

  1. #1
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    Changing the subject involving division

    What is my first move please?

    y=\frac{5+x}{1-x}
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  2. #2
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    Hello Meggomumsie
    Quote Originally Posted by Meggomumsie View Post
    What is my first move please?

    y=\frac{5+x}{1-x}
    Get rid of fractions - always a good move in handling any equation. So, multiply both sides by (1-x):

    y(1-x) = 5+x

    Then:

    • Remove brackets on the LHS


    • Collect terms in x on one side only; everything else on the other side


    • Take out a common factor of x (by writing x outside a bracket with the other bits inside)

    Divide both sides by the resulting bracket to make x the subject.

    Can you complete it now?

    Grandad
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  3. #3
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    Thank you for your answer. I would still be pondering without your prompts as I have not been taught to factorise in the middle of changing the subject of a formula. So here is my attempt.

    y=\frac{5+x}{1-x}

    y(1 - x) = 5 + x

    y - xy = 5 + x

    y -5 = x + xy

    y - 5 = x(1 + y)

    \frac{y-5}{y+1}=x

    It's great to be learning, thank you all ~ Marilyn
    Last edited by Meggomumsie; September 28th 2009 at 05:24 AM. Reason: Missed a stage
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  4. #4
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    Well done! Looks good to me.

    Grandad
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