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Math Help - Unsolvable problem?

  1. #1
    Junior Member
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    Unsolvable problem?

    3^x = 4x + 15

    Here's the farthest I can get:

    log(3^x) = log(4x + 15)

    xlog(3) = log(4x + 15)

    x = log(4x + 15)/log(3)

    Is graphing and finding the intersection point the only way to solve this?
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  2. #2
    MHF Contributor
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    Talking

    To my knowledge, this equation cannot be solved algebraically. You will have to use other methods. Sorry!
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  3. #3
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    e^(i*pi)'s Avatar
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    Quote Originally Posted by stapel View Post
    To my knowledge, this equation cannot be solved algebraically. You will have to use other methods. Sorry!
    Same, you'd need to iterate upon a solution.

    3^x = 4x + 15

    I plotted this graph (see below) and roughly arrived at x = -3.75 and x = 3.00.

    x = 3 is a solution but I got this from looking at the graph
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