Chapter 17: Problem 38
Solve the inequalities by displaying the solutions on a calculator. $$\ln (x-3) \geq 1$$
Short Answer
Expert verified
The solution is \( x \geq 5.71828 \).
Step by step solution
01
Understand the Inequality
The inequality is given as \( \ln (x-3) \geq 1 \). This means we want to find values of \( x \) such that the natural logarithm of \( x-3 \) is greater than or equal to 1.
02
Solve the Basic Inequality
To solve \( \ln(x-3) = 1 \), we need to exponentiate both sides to remove the natural logarithm. Doing so yields: \[ e^{\ln(x-3)} = e^1 \] Therefore, \( x-3 = e \), so \( x = e + 3 \).
03
Determine the Solution Set
The inequality \( \ln(x-3) \geq 1 \) implies \( x-3 \geq e \). Since \( e \approx 2.718 \), adding 3 gives \( x \geq 3 + e \).
04
Interpret on a Calculator
On a calculator, calculate \( e \) to several decimal places (\( e \approx 2.71828 \)) and add 3. Therefore, \( x \geq 5.71828 \) to at least five decimal places.
05
State the Solution
The solution to the inequality is all real numbers \( x \) such that \( x \geq 3 + e \). Therefore, the solution is \( x \geq 5.71828 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Natural Logarithm
The natural logarithm, represented as \( \ln \), is a logarithm to the base \( e \), where \( e \) is approximately equal to 2.71828. It is a mathematical function often used to describe exponential growth or decay processes. In simple terms, the natural logarithm answers the question: "To what power must \( e \) be raised, to obtain a given number?" For instance, if \( \ln(a) = b \), it means \( e^b = a \). This comes in handy when solving equations or inequalities involving logarithmic expressions.
- Key feature: \( \ln(e) = 1 \), because \( e^1 = e \).
- Useful property: \( \ln(xy) = \ln(x) + \ln(y) \).
Exponentiation
Exponentiation refers to the operation of raising a number (the base) to a certain power (the exponent). In the context of natural logarithms, exponentiation is used to "undo" the logarithm. When you have an equation like \( \ln(x-3) = 1 \), you can exponentiate both sides to eliminate the logarithm and solve for \( x \).
- Example: \( e^{\ln(x-3)} = e^1 \), simplifies to \( x-3 = e \).
- The operation is based on properties such as \( a^0 = 1 \) and \( a^1 = a \).
Inequality Solution
Solving an inequality involves finding all possible values of the variable that satisfy the given condition. In our exercise, the inequality was \( \ln (x-3) \geq 1 \). To solve it:1. First, find the critical point by equating \( \ln(x-3) = 1 \), leading to the point \( x = e + 3 \).2. Then, determine the range of \( x \) that satisfies \( \ln(x-3) \geq 1 \). This translates to \( x \geq e + 3 \), meaning \( x \) must be greater than or equal to this value.3. Using a calculator further refines this to \( x \geq 5.71828 \).Calculators can help verify or explore these solutions by providing accurate values for \( e \) and calculating the values to several decimal places.
Mathematical Solutions
Mathematical solutions often require multiple steps and techniques to arrive at a precise answer. With the inequality \( \ln(x-3) \geq 1 \), the analytical approach involves:- Understanding the role of each function, here \( \ln \) and exponentiation.- Calculating crucial constants like \( e \) to an adequate precision.- Verifying on a calculator can provide extra confidence, especially when dealing with transcendental numbers like \( e \).This solution process shows how different mathematical concepts align to provide a comprehensive understanding. Moreover, it's crucial to interpret results contextually, ensuring they fit within the given parameters of the problem.