Problem 16 - Algebra 2

Question

Solve each equation. Check your answers. $$ \ln (4 x-1)=36 $$

Step-by-Step Solution

Answer

The solution to the equation \(\ln (4x - 1) = 36\) is \(x = (e^{36} + 1) / 4\)

Step 1: Convert from Logarithmic to Exponential Form

To change the problem from its logarithmic form, \(\ln (4x - 1) = 36\), to exponential form, recall the definition of a logarithm. If \(b^y = x\), then \(\log_b (x) = y\). Using the log base \(e\), the equation then becomes \(e^{36} = 4x - 1\).

Step 2: Simplify the Equation

Calculate the value of \(e^{36}\). Then add 1 to both sides of the equation: \(e^{36} + 1 = 4x\).

Step 3: Solve for x

Following the simplification, the last step is to solve for \(x\). Do this by dividing both sides of the equation by 4: \((e^{36} + 1) / 4 = x\).

Key Concepts

Logarithmic Functions

Logarithmic functions are a fascinating mathematical concept often introduced as the inverse operations of exponential functions. This relationship can be structured as follows: if we have an exponential expression of the form \( b^y = x \), the logarithmic form would be \( \log_b(x) = y \). In logarithmic functions, \( b \) is the base, \( x \) is the argument, and \( y \) is the logarithm of \( x \) that we are solving for.

When the base \( b \) is the special number known as Euler’s number, \( e \), the function is referred to as a natural logarithm and is denoted by \( \ln(x) \). This base \( e \approx 2.71828 \) is important in many areas of mathematics and physics. Logarithmic functions, particularly natural logarithms, are used in calculations involving compound interest, growth equations, and in this case, equation solving.

Natural Logarithm

The natural logarithm is a specific type of logarithm where the base is \( e \), an irrational constant approximately equal to 2.71828. The notation for natural logarithm is \( \ln(x) \), where \( x \) must be a positive real number. The reason why \( e \) is used as a base is that it naturally arises in many mathematical scenarios, like growth processes and calculus.

Converting from a natural logarithm to an exponential function employs the formula \( x = e^y \), where \( y = \ln(x) \). In this process, transitioning from \( \ln(4x - 1) = 36 \) to its equivalent exponential form involves seeing it as \( e^{36} = 4x - 1 \).

Natural logarithms are pivotal when working with different types of growth models or decay processes in disciplines ranging from biology to financial mathematics.

Equation Solving

Equation solving is a critical skill in mathematics, allowing us to find unknown values within expressions. One common method involves isolating the variable of interest by rearranging and simplifying the equation. In the context of our example, after converting the logarithmic equation \( \ln(4x - 1) = 36 \) to its exponential counterpart, the task is to solve for \( x \).

Steps involved are:

• Start from \( e^{36} = 4x - 1 \). This hints that \( x \) is part of a rearranged exponential equation.
• Add 1 to both sides to further isolate the terms with \( x \): \( e^{36} + 1 = 4x \).
• Finally, divide both sides by 4 to solve for \( x \): \( x = \frac{e^{36} + 1}{4} \).

Understanding these steps is crucial as they form a pattern that recurs in different types of algebraic problems, and mastering them provides a handy toolkit for tackling complex real-world scenarios.