Example

Example 10.20: Evaluating Logarithmic Equations

Find the value of xx in the following logarithmic equations: ⓐ logx36=2\log_x 36 = 2log4x=3\log_4 x = 3log1218=x\log_{\frac{1}{2}} \frac{1}{8} = x

Solution Convert each logarithmic equation into its equivalent exponential form and solve for xx.

logx36=2\log_x 36 = 2 Convert to exponential form: x2=36x^2 = 36. Solve the quadratic equation: x=6x = 6 or x=6x = -6. The base of a logarithmic function must be positive, so eliminate x=6x = -6. Therefore, x=6x = 6, which means log636=2\log_6 36 = 2.

log4x=3\log_4 x = 3 Convert to exponential form: 43=x4^3 = x. Simplify the exponential expression: x=64x = 64. Therefore, log464=3\log_4 64 = 3.

log1218=x\log_{\frac{1}{2}} \frac{1}{8} = x Convert to exponential form: (12)x=18\left(\frac{1}{2}\right)^x = \frac{1}{8}. Rewrite 18\frac{1}{8} as a power of 12\frac{1}{2}: (12)x=(12)3\left(\frac{1}{2}\right)^x = \left(\frac{1}{2}\right)^3. With the same base, the exponents must be equal: x=3x = 3. Therefore, log1218=3\log_{\frac{1}{2}} \frac{1}{8} = 3.

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Updated 2026-05-26

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