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Ch. 4 - Inverse, Exponential, and Logarithmic Functions
Lial - College Algebra 13th Edition
Lial13th EditionCollege AlgebraISBN: 9780136881063Not the one you use?Change textbook
Chapter 5, Problem 35

Solve each equation. log9 x = 5/2

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1
Recognize that the equation is given in logarithmic form: \(\log_{9} x = \frac{5}{2}\). This means the logarithm base is 9, and the logarithm of \(x\) equals \(\frac{5}{2}\).
Recall the definition of logarithm: \(\log_{a} b = c\) means \(a^{c} = b\). Apply this to rewrite the equation as an exponential equation: \(9^{\frac{5}{2}} = x\).
Express the base 9 as a power of a smaller base if possible. Since \$9 = 3^{2}$, rewrite \(9^{\frac{5}{2}}\) as \((3^{2})^{\frac{5}{2}}\).
Use the power of a power property: \((a^{m})^{n} = a^{m \times n}\). So, \((3^{2})^{\frac{5}{2}} = 3^{2 \times \frac{5}{2}}\).
Simplify the exponent multiplication: \(2 \times \frac{5}{2} = 5\). Therefore, \(x = 3^{5}\). This expresses the solution for \(x\) in exponential form.

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Key Concepts

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

Logarithmic Functions

A logarithmic function is the inverse of an exponential function. It answers the question: to what power must the base be raised to produce a given number? For example, log₉(x) = y means 9 raised to y equals x.
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Graphs of Logarithmic Functions

Properties of Logarithms

Understanding properties like the definition of logarithms and how to rewrite logarithmic equations in exponential form is essential. For instance, logₐ(b) = c can be rewritten as a^c = b, which helps in solving equations.
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Change of Base Property

Solving Exponential Equations

Once the logarithmic equation is converted to exponential form, solving involves applying exponent rules and algebraic manipulation to isolate the variable. This step is crucial to find the exact value of x.
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Solving Exponential Equations Using Logs