Chapter 4: Problem 64
Solve the inequality. $$3 \leq \log _{2} x \leq 4$$
Short Answer
Expert verified
The solution is \( x \in [8, 16] \).
Step by step solution
01
Understand the Inequality
The inequality given is \( 3 \leq \log_{2} x \leq 4 \). This means that the base 2 logarithm of \( x \) is bounded between 3 and 4.
02
Convert the Inequality to Exponential Form
To solve \( 3 \leq \log_{2} x \leq 4 \), convert the inequality to exponential form using the property of logarithms that states if \( \log_{b}(a)=c \) then \( a=b^{c} \). Therefore, the inequality becomes \( 2^{3} \leq x \leq 2^{4} \).
03
Calculate the Exponents
Now compute the exponents: \( 2^{3} = 8 \) and \( 2^{4} = 16 \). Therefore, we now have \( 8 \leq x \leq 16 \).
04
Conclusion: Interval of Solutions
The interval that satisfies the original inequality is \( x \in [8, 16] \). This means \( x \) can take any value from 8 to 16, inclusive.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Form
When dealing with logarithmic inequalities, converting them into exponential form is a crucial step that often simplifies the problem significantly. In the case of the inequality \( 3 \leq \log_{2} x \leq 4 \), understanding how to transition from logarithmic to exponential form is essential.
The key principle at work here is the definition of a logarithm. Specifically, if \( \log_{b}(a) = c \), it implies that \( a = b^{c} \). This transition from a logarithmic to an exponential expression allows us to view the problem in a different light that can be more intuitive. In our current problem, applying this definition helps to transform the inequality into \( 2^{3} \leq x \leq 2^{4} \).
In essence, converting to exponential form makes it straightforward to solve for \( x \) because the logarithm's base gives us the exponential base, and the inequality bounds give us the exponents. This transformation is not only a conversion of forms but also a simplification step that provides a clear path to finding the solution of the inequality, which in this case, results in \( 8 \leq x \leq 16 \).
The key principle at work here is the definition of a logarithm. Specifically, if \( \log_{b}(a) = c \), it implies that \( a = b^{c} \). This transition from a logarithmic to an exponential expression allows us to view the problem in a different light that can be more intuitive. In our current problem, applying this definition helps to transform the inequality into \( 2^{3} \leq x \leq 2^{4} \).
In essence, converting to exponential form makes it straightforward to solve for \( x \) because the logarithm's base gives us the exponential base, and the inequality bounds give us the exponents. This transformation is not only a conversion of forms but also a simplification step that provides a clear path to finding the solution of the inequality, which in this case, results in \( 8 \leq x \leq 16 \).
Logarithms
Logarithms are powerful mathematical tools that help us manage exponential relationships. At their core, they answer the question: "To what exponent must a base be raised, to obtain a specific number?"
In the inequality \( 3 \leq \log_{2} x \leq 4 \), \( \log_{2} x \) is the logarithm with base 2 of the number \( x \). It tells us the power to which 2 must be raised to equal \( x \). For example, if \( \log_{2} x = 3 \), then \( x = 2^{3} = 8 \).
A few key properties of logarithms can be incredibly useful when dealing with inequalities:
In the inequality \( 3 \leq \log_{2} x \leq 4 \), \( \log_{2} x \) is the logarithm with base 2 of the number \( x \). It tells us the power to which 2 must be raised to equal \( x \). For example, if \( \log_{2} x = 3 \), then \( x = 2^{3} = 8 \).
A few key properties of logarithms can be incredibly useful when dealing with inequalities:
- If \( \log_{b}(a) = c \), then \( a = b^{c} \).
- Logarithms turn multiplication into addition: \( \log_{b}(mn) = \log_{b}(m) + \log_{b}(n) \).
- Logarithms turn division into subtraction: \( \log_{b}(\frac{m}{n}) = \log_{b}(m) - \log_{b}(n) \).
Inequality Solutions
Solving inequalities involves not only finding values that work with the equality, but also determining a range of values that satisfy the entire inequality. With logarithmic inequalities, as given in the problem \( 3 \leq \log_{2} x \leq 4 \), the goal is to find all possible values of \( x \) that make this statement true.
Once the inequality is converted to exponential form, it becomes much simpler. We discovered that \( 2^{3} \leq x \leq 2^{4} \) simplifies the problem to finding the interval \( 8 \leq x \leq 16 \).
This interval tells us that any value of \( x \), including 8 and 16 itself, will satisfy the original statement. Here are a few considerations when dealing with inequality solutions:
Once the inequality is converted to exponential form, it becomes much simpler. We discovered that \( 2^{3} \leq x \leq 2^{4} \) simplifies the problem to finding the interval \( 8 \leq x \leq 16 \).
This interval tells us that any value of \( x \), including 8 and 16 itself, will satisfy the original statement. Here are a few considerations when dealing with inequality solutions:
- Always remember to include all values within the range, as specified by the inequality.
- Consider whether endpoints like the values 8 and 16 are included, as they play crucial roles in inequality boundaries.
- Double check solutions by substituting values back into the original equation to ensure they satisfy the inequality.