Chapter 4: Problem 26
Use the definition of the logarithmic function to find \(x .\) (a) \(\log _{5} x=4\) (b) \(\log _{10} 0.1=x\)
Short Answer
Expert verified
(a) \( x = 625 \), (b) \( x = -1 \)
Step by step solution
01
Understand the Problem for Part (a)
We need to find the value of \( x \) such that the logarithmic equation \( \log_{5} x = 4 \) is satisfied. This means we need to rewrite the equation in its exponential form.
02
Convert to Exponential Form for Part (a)
The equation \( \log_{5} x = 4 \) can be converted to exponential form using the definition of logarithms: If \( \log_{b} a = c \), then \( b^{c} = a \). Applying this, we get: \[ x = 5^{4} \].
03
Calculate for Part (a)
Calculate \( 5^{4} \):\[ 5^{4} = 5 \times 5 \times 5 \times 5 = 625 \]Thus, \( x = 625 \).
04
Understand the Problem for Part (b)
In part (b), we need to find the value of \( x \) such that \( \log_{10} 0.1 = x \).
05
Convert to Exponential Form for Part (b)
The equation \( \log_{10} 0.1 = x \) can be rewritten in exponential form as \( 10^{x} = 0.1 \).
06
Solve for x in Part (b)
To find \( x \), we note that \( 0.1 = \frac{1}{10} = 10^{-1} \). Therefore, we have: \[ 10^{x} = 10^{-1} \] By comparing the exponents, we find that \( x = -1 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Form
Understanding how to convert from a logarithmic equation to exponential form is a fundamental skill when dealing with logarithmic functions. The relationship between these two forms is crucial. If you have the logarithmic equation \( \log_{b} a = c \), it means "what power must we raise \( b \) to get \( a \)?" Converting this to exponential form helps us see this more clearly:
That is why understanding exponential form is a powerful tool in solving logarithmic problems.
- Start with \( \log_{b} a = c \).
- Recognize that this is equivalent to saying \( b^{c} = a \).
That is why understanding exponential form is a powerful tool in solving logarithmic problems.
Logarithmic Equations
Logarithmic equations are equations that involve a logarithm with a variable inside it, such as \( \log_{b} x = y \). Solving these equations often requires a technique known as converting the equation to its exponential form. Recognizing this opportunity for conversion is essential, because it simplifies the calculation and allows us to solve for the unknown.
- Isolate the logarithmic expression if necessary.
- Convert the logarithm to an exponential equation.
- Solve the resulting equation for the variable.
Definition of Logarithms
The logarithm of a number is a mathematical concept that indicates the power to which a base number is raised to obtain that number. Basically, if \( b^c = a \), then \( \log_{b} a = c \). This definition helps us understand logarithms extensively.
- \( b \) is called the base.
- \( a \) is the number we are taking the logarithm of.
- \( c \) is the logarithm and tells us the power we need.