Example

Try It 10.47: Solving loga121=2\log_a 121 = 2 and lnx=7\ln x = 7

To solve the logarithmic equations loga121=2\log_a 121 = 2 and lnx=7\ln x = 7, convert each into its corresponding exponential form. For loga121=2\log_a 121 = 2, the equivalent exponential form is a2=121a^2 = 121. Solving for aa using the square root property yields potential solutions of a=11a = 11 and a=11a = -11. Since a logarithmic base must be positive, the negative value is an extraneous solution, meaning the only valid answer is a=11a = 11. For the natural logarithmic equation lnx=7\ln x = 7, rewriting it into exponential form directly yields x=e7x = e^7. Thus, the exact solution is x=e7x = e^7.

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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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