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Example 10.41: Solving 5x=115^x = 11

To solve the exponential equation 5x=115^x = 11, where the bases cannot be made identical, take the common logarithm of both sides to get log5x=log11\log 5^x = \log 11. Apply the Power Property of Logarithms to move the exponent xx to the front, yielding xlog5=log11x \log 5 = \log 11. Divide both sides by log5\log 5 to find the exact solution x=log11log5x = \frac{\log 11}{\log 5}. Using a calculator, this value approximates to 1.4901.490. To check if this makes sense, observe that 51=55^1 = 5 and 52=255^2 = 25, so 51.490115^{1.490} \approx 11 is reasonable.

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Updated 2026-05-25

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Ch.10 Exponential and Logarithmic Functions - Intermediate Algebra @ OpenStax

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