/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 86 Let \(\log _{b} 2=A\) and \(\log... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

Let \(\log _{b} 2=A\) and \(\log _{b} 3=C .\) Write each expression in terms of \(A\) and \(C\). $$\log _{b} 81$$

Short Answer

Expert verified
The expression \(\log_b81\) written in terms of \(A\) and \(C\) is \(4C\).

Step by step solution

01

Break Down the Number

Break down the number 81 into its prime factors. As 81 is 3 raised to the power of 4 (\(3^4\)), the log expression becomes \(\log_b{3^4}\)
02

Apply the Power Rule

Applying the power rule of logarithms, which states that \(\log_b{M^n} = n \log_b{M}\), the expression transforms to \(4*\log_b{3}\)
03

Replace \(\log_b{3}\) with C

Replace the \(\log_b{3}\) in the last step with given variable \(C\) resulting in \(4*C\)

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Power Rule of Logarithms
Understanding the power rule of logarithms is essential for simplifying logarithmic expressions. Simply put, if you have a logarithm of a number raised to a power, such as \(\log_b{M^n} \), you can 'bring down' the exponent and multiply it by the logarithm of the base number, effectively transforming it to \(n \log_b{M}\).
For students grappling with logarithms, the power rule is quite handy. For example, if we have \(\log_b{81}\) and know that 81 is \(3^4\), the power rule allows us to rewrite this as \(4 \log_b{3}\), which looks neater and is much easier to work with, especially when you need to use given variables like \(A\) and \(C\) to express your answer.
Prime Factorization
Prime factorization is the process of breaking down a composite number into its prime factors. Prime numbers are the building blocks of all integers, with each composite number having a unique combination of prime factors.
This concept is particularly useful when simplifying logarithmic expressions, because once a number is broken down into its prime factors, you can apply logarithmic identities, including the power rule. Take the number 81 from the original exercise: its prime factorization is \(3^4\), meaning that the number 81 is three multiplied by itself four times. Here, \(3\) is a prime number, and the exponent \(4\) represents how many times it's used as a factor.
When prime factorization is mentioned in a logarithmic problem, it's often the key to unlocking a simpler form and therefore, a clearer path to the solution.
Logarithms and Exponents
Logarithms and exponents are closely related, as logarithms are essentially the inverses of exponential functions. In other words, if \(b^x = y\), then \(\log_b{y} = x\). This inverse relationship is crucial for solving equations involving exponents and for understanding how logarithmic expressions work.
This concept comes into play when you are given logarithmic expressions with a base and have to find their connection to exponential forms. In the context of the exercise, knowing that \(\log_b{2} = A\) and \(\log_b{3} = C\), essentially tells you that \(b^A = 2\) and \(b^C = 3\), offering a clear way to convert between logarithmic and exponential forms and to perform substitutions and simplifications with variables.

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