Problem 11 - College Algebra and Calculus: An Applied Approach

Question

Write the logarithm in terms of common logarithms.\(\log _{2.6} x\)

Step-by-Step Solution

Answer

In terms of common logarithms, \( \log _{2.6} x = \log x / \log 2.6 \).

Step 1: Identify the given logarithm

The problem provides the logarithm: \( \log _{2.6} x \). Here, 2.6 is the base and x is the argument of the logarithm.

Step 2: Use the change of base formula

Apply the change of base formula to rewrite \( \log _{2.6} x \) in terms of common logarithms. The formula is: logb(a) = logc(a) / logc(b), where c is the base to change to. Since a common logarithm is a logarithm with base 10, the formula for this problem becomes: \( \log _{2.6} x = \log _{10} x / \log _{10} 2.6 \).

Step 3: Simplify the expression

Since the log with base 10 is the common logarithm, it's usually written without the subscripted base: \( \log _{10} x = \log x \) and \( \log _{10} 2.6 = \log 2.6 \). Therefore, the expression \( \log _{2.6} x \) in terms of common logarithms is: \( \log _{2.6} x = \log x / \log 2.6 \).

Key Concepts

Common Logarithms

When we refer to common logarithms, we're talking about logarithms that have a base of 10. These are so commonly used in mathematics and science that they are often just written as \( \log x \) without the base indicated, implicitly understood to be 10. In practice, common logarithms can help simplify complex calculations involving exponential growth, such as in finance with compound interest, or in science when dealing with the pH scale.

Interestingly, they also form the foundation for the logarithmic scale, which measures the relative intensity of sound and earthquakes. It's crucial to recognize that any logarithm can be converted to a common logarithm using the change of base formula, which is especially handy with calculators that may only have buttons for base 10 or base e logarithms.

Logarithmic Functions

Logarithmic functions are the inverse functions of exponential functions, meaning they undo the operation of exponentiation. If you have an equation of the form \( y = b^x \), its inverse would be \( x = \log_b y \). This inverse relationship is central to understanding how they work.

The function \( \log_b x \) answers the question: 'To what power do we raise b to obtain x?'. This makes logarithmic functions particularly useful in solving real-world problems where we need to find an unknown exponent, such as in radioactive decay or in computing algorithms for data processing. They're also pivotal in fields like acoustics, astronomy, and information theory.

Algebraic Manipulation

Algebraic manipulation refers to the process of rearranging and simplifying algebraic expressions and equations using a variety of operations and techniques. Common operations include adding, subtracting, multiplying, dividing, factoring, expanding, and applying rules of exponents and logarithms.

One such technique is using the change of base formula during the process of solving logarithmic equations, which is a quintessential example of algebraic manipulation. This formula allows us to rewrite expressions with bases that may not be directly calculable into a form that is more easily computed. Mastery of algebraic manipulation is a key skill in mathematics as it enables one to tackle a wide range of problems by transforming them into more manageable forms.