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Math Help - I don't see how my book solved for x.... can anyone help?

  1. #1
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    I don't see how my book solved for x.... can anyone help?

    x=ay
    y=x+10
    plugging it in x= a(x+10)

    the book SAYS solving for x yields x= 10a/(1-a)

    for the life of me I can't see how they got that.

    I tried multiplying by its reciprocal, working around it.... I just cant see it for the life of me.

    the book's solution doesn't show this step. is there something really basic I'm overlooking?
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  2. #2
    Senior Member nikhil's Avatar
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    x=ay
    y=x+10
    so
    x=a(x+10)
    x=ax+10a
    x-ax=10a
    x(1-a)=10a
    x=(10a)/(1-a)
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  3. #3
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    Quote Originally Posted by NotTooKeen View Post
    x=ay
    y=x+10
    plugging it in x= a(x+10)

    the book SAYS solving for x yields x= 10a/(1-a)

    for the life of me I can't see how they got that.

    I tried multiplying by its reciprocal, working around it.... I just cant see it for the life of me.

    the book's solution doesn't show this step. is there something really basic I'm overlooking?
    x = a(x + 10)

    x = ax + 10a

    x - ax = 10a

    x(1 - a) = 10a

    x = \frac{10a}{1 - a}.
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  4. #4
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    oh wow that was so simple I can't believe it.

    do you guys have any tips on trying to catch obvious things like that?

    I'm so oblivious sometimes, but I have a study sheet and go over the rules every day. I just manage to overlook them somehow...

    thanks for the help, by the way
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  5. #5
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    Quote Originally Posted by NotTooKeen View Post
    oh wow that was so simple I can't believe it.

    do you guys have any tips on trying to catch obvious things like that?

    I'm so oblivious sometimes, but I have a study sheet and go over the rules every day. I just manage to overlook them somehow...

    thanks for the help, by the way
    Lots and lots of practice.
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