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Ch. 4 - Exponential and Logarithmic Functions
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 5, Problem 15

Write each equation in its equivalent exponential form. log3 81 = y

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Recall the definition of logarithm: \( \log_b a = c \) means \( b^c = a \).
Identify the base \( b \), the result \( a \), and the logarithm value \( c \) from the equation \( \log_3 81 = y \). Here, \( b = 3 \), \( a = 81 \), and \( c = y \).
Rewrite the logarithmic equation \( \log_3 81 = y \) in its equivalent exponential form using the definition: \( 3^y = 81 \).
This expresses the original logarithmic equation as an exponential equation, which is the required equivalent form.
You can verify this by recognizing that \( 81 \) is a power of \( 3 \), but the problem only asks for the equivalent exponential form, so no further calculation is needed.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Definition of Logarithms

A logarithm answers the question: to what exponent must the base be raised to produce a given number? For example, log3 81 = y means 3 raised to the power y equals 81. Understanding this definition is essential to convert between logarithmic and exponential forms.
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Exponential Form of a Logarithmic Equation

The exponential form of a logarithmic equation log_b a = c is b^c = a. This conversion is fundamental because it allows solving logarithmic equations by rewriting them as exponential equations, making it easier to find unknown exponents or values.
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Solving Logarithmic Equations

Properties of Exponents and Powers

Recognizing powers of numbers helps simplify and solve equations. For instance, knowing that 81 = 3^4 allows you to rewrite log3 81 = y as 3^y = 3^4, leading to y = 4. Familiarity with exponent rules aids in identifying equivalent expressions.
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