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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 87

Let logb 2 = A and logb 3 = C and Write each expression in terms of A and C. logb √(2/27)

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Start by expressing the argument inside the logarithm in terms of powers: \( \sqrt{\frac{2}{27}} = \left( \frac{2}{27} \right)^{\frac{1}{2}} \).
Rewrite the fraction inside the parentheses as a quotient of powers: \( \left( \frac{2}{3^3} \right)^{\frac{1}{2}} \) since \(27 = 3^3\).
Apply the logarithm power rule: \( \log_b \left( \frac{2}{3^3} \right)^{\frac{1}{2}} = \frac{1}{2} \log_b \left( \frac{2}{3^3} \right) \).
Use the logarithm quotient rule: \( \log_b \left( \frac{2}{3^3} \right) = \log_b 2 - \log_b 3^3 \).
Apply the logarithm power rule again: \( \log_b 3^3 = 3 \log_b 3 \). Now substitute \( \log_b 2 = A \) and \( \log_b 3 = C \) to write the expression entirely in terms of \( A \) and \( C \).

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Key Concepts

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

Properties of Logarithms

Logarithms have specific properties such as the product, quotient, and power rules. These allow us to rewrite complex logarithmic expressions as sums, differences, or multiples of simpler logarithms, which is essential for expressing the given log in terms of A and C.
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Change of Base Property

Change of Base and Given Logarithm Values

The problem provides logb 2 = A and logb 3 = C, which means logarithms of 2 and 3 with base b are known. Using these values, we can express other logarithms involving 2 and 3 by breaking down numbers into prime factors and substituting A and C accordingly.
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Change of Base Property

Simplifying Radicals and Fractions Inside Logarithms

The expression involves a square root and a fraction inside the logarithm. Understanding how to rewrite radicals as fractional exponents and how to separate logarithms of quotients helps in breaking down the expression into parts that can be expressed using A and C.
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Radical Expressions with Fractions