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12 September, 20:43

3^x+1=5^x-4 what is x?

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Answers (2)
  1. 12 September, 21:12
    0
    3^x+1=5^x-4 what is x? X=3

    3^x+1=5^3-4
  2. 12 September, 23:16
    0
    Hello from MrBillDoesMath!

    Answer: 14.75330052 ...

    Discussion: Per the author the equation should be interpreted as

    3 ^ (x+1) = 5^ (x-4)

    NOT as (3^x) + 1 = (5^x) - 4

    Rewrite the equation to pull out the constant terms:

    3^ (x+1) = 3^x * 3^1 = 3^x * 3 = 5^x * (5^-4)

    so 3^x * 3 = 5^x * (5^-4)

    Divide both sides by 3 to get

    3^x * = 5^x * ((5^-4) / 3)

    Divide both sides by 5^x to get

    (3/5) ^ x = (1/625 * 1/3) = 1/1875

    Take the base 10 logarithm (is this middle school math?) of each side

    x * log (3/5) = log (1/1875) or (taking log. bring exponent down)

    x = log (1/1875) / log (3/5)

    so

    x = (-3.273001272) / - 0.22184875

    which gives x as approx 14.75

    I suspect there is still something wrong in the problem statement as I'm skeptical that this is middle level math.

    Regards, MrB
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