Chapter 4: Problem 343
Solve the equation for \(x,\) if there is a solution. Then graph both sides of the equation, and observe the point of intersection (if it exists) to verify the solution. \(\ln (3 x)=2\)
Short Answer
Expert verified
The solution is \( x = \frac{e^2}{3} \). The intersection of the graphs at this \( x \)-value verifies the solution.
Step by step solution
01
Understand the Equation
The given equation is \( \ln(3x) = 2 \). Here, \( \ln \) is the natural logarithm function, which means we're looking for the value of \( x \) such that when 3 times \( x \) is taken as the argument of the natural logarithm, the result is 2.
02
Exponentiate Both Sides
To solve for \( x \), we exponentiate both sides of the equation. The inverse operation of natural logarithm is the exponential function. Thus, we raise both sides as powers of \( e \) (Euler's number):\[ e^{\ln(3x)} = e^2 \]. This simplifies to \( 3x = e^2 \), because \( e^{\ln(a)} = a \) for any \( a \).
03
Solve for x
After simplifying, the equation becomes \( 3x = e^2 \). To isolate \( x \), divide both sides by 3:\[ x = \frac{e^2}{3} \]. This is the solution for \( x \).
04
Graph the Functions
Graph the functions \( y = \ln(3x) \) and \( y = 2 \) on the same set of axes. The function \( y = \ln(3x) \) will be a logarithmic curve, and \( y = 2 \) will be a horizontal line. Plotting these functions will show where they intersect.
05
Verify the Solution with Intersection
The point where the graphs intersect represents the solution to the equation. The \( x \)-coordinate of this intersection point should be \( x = \frac{e^2}{3} \). If the graphs intersect at this \( x \)-value, the solution is verified.
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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, often denoted as \( \ln \), is a fundamental concept in mathematics associated with exponential growth and decay. A natural logarithm is a logarithm to the base \( e \), where \( e \) is an irrational constant approximately equal to 2.71828. It provides a useful way to express time in processes that grow or reduce at a rate proportional to their size. For example, in our equation \( \ln(3x) = 2 \), \( \ln \) tells us that the power to which you must raise \( e \) to obtain \( 3x \) is precisely 2. Understanding the natural logarithm is crucial for solving equations involving exponential relationships, as it often serves as a bridge between multiplicative and additive operations. - Logarithms are inverse exponentials. - The notation \( \ln(a) = b \) implies \( e^b = a \). Using these properties helps in simplifying and rearranging complex equations and finding unknowns efficiently.
Exponential Function
The exponential function plays a critical role in solving equations that involve logarithms, particularly natural logarithms. This function is denoted as \( e^x \), where \( e \) is Euler's number. It's the inverse function of the natural logarithm. In the exponential function, the input \( x \) is the exponent or power to which \( e \) is raised. Many natural phenomena, such as population growth and radioactive decay, follow exponential patterns, making the exponential function widely applicable.In our equation \( \ln(3x) = 2 \), once we apply the exponential function to both sides, we revert from the logarithmic form to exponential form: \( e^{\ln(3x)} = e^2 \). This step simplifies the equation to \( 3x = e^2 \), highlighting how exponential and logarithmic operations are tightly interconnected and how they simplify equations effectively.
Graphing Intersections
Graphing is a visual method to solve equations and verify solutions. By plotting equations on a graph, we can better understand their behavior and identify solutions as intersection points. For this exercise, graphing \( y = \ln(3x) \) and \( y = 2 \) can visually verify the algebraic solution. - \( y = \ln(3x) \) forms a curve that approaches but never touches the vertical axis. It increases slowly as \( x \) grows.- \( y = 2 \) is a horizontal line, indicating that no matter the value of \( x \), \( y \) remains constant at 2.The solution \( x = \frac{e^2}{3} \) is where these graphs intersect. This means that both functions share the same value at this specific \( x \)-coordinate, confirming the solution graphically. The intersection provides a useful reality check on algebraic results, making graphing a powerful tool for visualization and verification.
Algebraic Manipulation
Algebraic manipulation involves rearranging and simplifying equations to find unknown variables like \( x \). In our problem, algebraic steps are used to isolate \( x \) by performing operations that reverse the original processes applied in forming the equation. It's essential to apply these operations accurately to maintain the integrity of the equation.- Begin with \( \ln(3x) = 2 \).- Apply exponentiation to both sides to counter the logarithm: \( e^{\ln(3x)} = e^2 \), simplifying to \( 3x = e^2 \).- Finally, divide by 3 to isolate \( x \): \( x = \frac{e^2}{3} \).These steps demonstrate the reverse operations of what was initially applied, leveraging both the properties of logarithms and exponentials. Mastery of such techniques is essential for solving a broad range of mathematical problems efficiently.