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Math Help - Solving an exponential equation with two unknowns

  1. #1
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    Exclamation Solving an exponential equation with two unknowns

    solve the following system:

    2^(x+3y) = 128
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  2. #2
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    Quote Originally Posted by math123456 View Post
    solve the following system:

    2^(x+3y) = 128
    Start by solving x + 3y = 7.
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  3. #3
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    Not 100% sure here, but.

    To solve for y.

    Rewrite 128 as 2 to the something power, which is:

    2 to the 7th power.

    Set x+3y equal to 7.

    x+3y = 7
    3y = -x + 7
    y = -(x-7)/3

    Same for x, except solve x+3y = 7 for x.
    x = -3y + 7

    I believe this is how it's done.
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  4. #4
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    Quote Originally Posted by IAmLegendToo View Post
    Not 100% sure here, but.

    To solve for y.

    Rewrite 128 as 2 to the something power, which is:

    2 to the 7th power.

    Set x+3y equal to 7.

    x+3y = 7
    3y = -x + 7
    y = -(x-7)/3

    Same for x, except solve x+3y = 7 for x.
    x = -3y + 7

    I believe this is how it's done.
    Because there are 2 variables in the one equation there will be infinite solutions that lie on the line

    y =\frac{-x}{3}+=\frac{7}{3}
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  5. #5
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    You said, in your first post, "Solve the following system" (my emphasis). You did not give a system. What does the problem really say?
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