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Interpret logarithms as exponents

A logarithm represents the exponent required to produce a positive number from a specified positive base: logb(a)=c\log_b(a)=c precisely when bc=ab^c=a, with b>0b>0, b1b\ne1, and a>0a>0. This inverse relationship enables interpretation and solution of exponential equations, including integer, fractional, and negative exponents, while excluding complex logarithms and more advanced properties or applications beyond real-number relationships.

Detailed Explanation: Interpret logarithms as exponents

A logarithm tells you the exponent needed to produce a number:

logb(a)=cbc=a\log_b(a)=c \quad \Longleftrightarrow \quad b^c=a

Here, bb is the positive base, aa is the positive number inside the logarithm, and cc is the exponent.

Example: Find log2(18)\log_2\left(\frac18\right).

Let

x=log2(18).x=\log_2\left(\frac18\right).

Use the definition of a logarithm to rewrite this as an exponential equation:

2x=18.2^x=\frac18.

Rewrite 18\frac18 as a power of 22:

18=123=23.\frac18=\frac{1}{2^3}=2^{-3}.

Therefore,

2x=23.2^x=2^{-3}.

Since the bases are the same, the exponents must be equal:

x=3.x=-3.

So,

log2(18)=3.\boxed{\log_2\left(\frac18\right)=-3}.

This means that the exponent required to produce 18\frac18 from base 22 is 3-3, because

23=18.2^{-3}=\frac18.

Learn by doing: Interpret logarithms as exponents

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Logarithms - Convert Logarithm to Exponent - Natural Base


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