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Math Help - combining functions question 4

  1. #1
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    Exclamation combining functions question 4

    Increasing x by y% gives 12. Decreasing x by y% gives 8. Deteremine the value of x.
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  2. #2
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    Hello, math123456!

    I don't see how this relates to "combining functions."
    It is straight algebra . . .


    Increasing x by y% gives 12.
    Decreasing x by y% gives 8.
    Deteremine the value of x.

    We have: . \begin{array}{cccccccc}x(1+y) &=& 12 & \Longrightarrow & x + xy &=& 12 & {\color{blue}[1]} \\<br />
x(1-y) &=& 8 & \Longrightarrow & x - xy &=& 8 & {\color{blue}[2]} \end{array}

    Add [1] and [2]: . x \:=\:20 \quad\Rightarrow\quad\boxed{x \:=\:10}

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