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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 85

In Exercises 83–88, let logb 2 = A and logb 3 = C and Write each expression in terms of A and C.
logb 8

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1
Recognize that the expression log_b 8 can be rewritten using the fact that 8 is a power of 2. Since 8 = 2^3, rewrite the logarithm as log_b (2^3).
Apply the logarithmic power rule, which states that log_b (x^n) = n * log_b x. Using this, rewrite log_b (2^3) as 3 * log_b 2.
Recall the given information that log_b 2 = A. Substitute this into the expression to get 3 * A.
Thus, the expression log_b 8 is written in terms of A as 3A.
No further simplification is needed since the problem asks to express the logarithm 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.

Logarithm Properties

Logarithms have specific properties such as the product, quotient, and power rules. The power rule states that log_b(x^n) = n * log_b(x), which allows us to simplify expressions like log_b(8) by expressing 8 as a power of a base number.
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Change of Base Property

Change of Base and Given Logarithms

When given specific logarithmic values like log_b(2) = A and log_b(3) = C, we can rewrite other logarithms in terms of these known values by expressing the argument as products or powers of 2 and 3. This helps in expressing complex logs in simpler terms.
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Change of Base Property

Prime Factorization

Prime factorization involves expressing a number as a product of prime numbers. For example, 8 can be written as 2^3. This factorization is essential to rewrite log_b(8) in terms of log_b(2), which is given as A, enabling simplification using logarithm properties.
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Introduction to Factoring Polynomials