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Solving this Logarithmic Function?

3^(2x+1) - 7 * 3^x + 4 = 0

please help!

4 Answers

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  • Anonymous
    1 decade ago
    Favorite Answer

    Note that:

    3^(2x + 1) - 7(3^x) + 4 = 0

    ==> [3^(2x) * 3^1] - 7(3^x) + 4 = 0

    ==> 3[3^(2x)] - 7(3^x) + 4 = 0.

    Letting u = 3^x yields:

    3u^2 - 7u + 4 = 0

    ==> (3u - 4)(u - 1) = 0

    ==> u = 4/3 and u = 1.

    Then since u = 3^x, we see that:

    3^x = 4/3 ==> x = log₃(4/3)/3 ≈ 0.087

    3^x = 1 ==> 3^x = 3^0 ==> x = 0.

    I hope this helps!

  • Philo
    Lv 7
    1 decade ago

    when x = 0 you have 3¹ - 7•3º + 4 = 3 - 7 + 4 = 0

    graphing suggests no other solutions

  • ?
    Lv 4
    4 years ago

    the common logarithmic function has a base of 10. As you extra your study you will see that different logarithmic applications could have a base such by way of fact the extensive type 2 and could be written as log(base small 2)x. The inverse of the log is exponentiation. hence, if the backside is ten you will possibly have 10^(y/3). additionally be conscious that by way of fact the backside differences so will the exponential. So if it have been 2, it may be 2^(x-a million) or despite.

  • Anonymous
    1 decade ago

    There are 2 roots:

    x = 0

    and

    x = log(4) / log(3) - 1

    (solve the equation as if it was a second degree equation where the variable is 3^x)

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