Skill: Apply the power law of logarithms

Explanation and Free Practice Resources

For a logarithm with base b>0b>0, b≠1b\ne1, and positive xx, the power law log⁡b(xp)=plog⁡b(x)\log_b(x^p)=p\log_b(x) expresses how logarithms convert exponents into multiplicative factors, supporting symbolic simplification and solving exponential equations. At this level, it applies to familiar integer and rational powers with valid positive domains; it does not include complex-valued logarithms or more advanced generalizations.

Detailed Explanation: Apply the power law of logarithms

The power law of logarithms lets you move an exponent from inside a logarithm to the front:

log⁡b(xp)=plog⁡b(x)\log_b(x^p)=p\log_b(x)

Here, b>0b>0, b≠1b\ne 1, and x>0x>0. The exponent becomes a multiplier; it does not stay inside the logarithm.

Worked example

Simplify

log⁡7((x2)3),x>0.\log_7\left((x^2)^3\right), \qquad x>0.

Step 1: Apply the power law to the outer exponent.

log⁡7((x2)3)=3log⁡7(x2)\log_7\left((x^2)^3\right)=3\log_7(x^2)

Step 2: Apply the power law again to x2x^2.

3log⁡7(x2)=3(2log⁡7x)3\log_7(x^2)=3\left(2\log_7 x\right)

Step 3: Multiply the numerical factors.

3(2log⁡7x)=6log⁡7x3\left(2\log_7 x\right)=6\log_7 x

Therefore,

log⁡7((x2)3)=6log⁡7x\boxed{\log_7\left((x^2)^3\right)=6\log_7 x}

The two exponents, 33 and 22, become factors in front of the logarithm.

Learn by doing: Apply the power law of logarithms

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Logarithms - Power Property - Power To Product (Integers)


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