Chapter 8: Problem 86
Solve each equation. If necessary, round to the nearest ten-thousandth. $$ \log _{8}(2 x-1)=\frac{1}{3} $$
Short Answer
Expert verified
x = 1.5
Step by step solution
01
Write in exponential form
The given equation is \( \log _{8}(2 x-1)=\frac{1}{3} \). By converting it into exponential form, the equation becomes \( 8^{\frac{1}{3}} = 2 x - 1 \). This stems from the rule that \( \log _{b}(x) = y \) can be written as \( b^{y} = x \).
02
Calculate Base to the Power
Next is to calculate \( 8^{\frac{1}{3}} \). This operation represents the cube root of 8, which is equal to 2. Therefore, our equation now becomes \( 2 = 2 x - 1 \).
03
Solve for \( x \)
Finally, solve the equation \( 2 = 2 x - 1 \) for \( x \). Adding 1 to both sides gives \( 3 = 2x \). Dividing both sides by 2 gives \( x = 1.5 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Form
The exponential form of a logarithmic equation offers a different way to express the relationship between numbers. In our problem, we start by having the logarithmic equation \( \log _{8}(2 x-1)=\frac{1}{3} \).
This can be confusing if you're not familiar with how logs work. By converting this into exponential form, it becomes \( 8^{\frac{1}{3}} = 2x - 1 \).
So how do we go from a log equation to exponential form? It's actually easier than it sounds:
This can be confusing if you're not familiar with how logs work. By converting this into exponential form, it becomes \( 8^{\frac{1}{3}} = 2x - 1 \).
So how do we go from a log equation to exponential form? It's actually easier than it sounds:
- The base of the logarithm (which is 8 here) stays the base in the exponential form.
- The result of the logarithmic function (\( \frac{1}{3} \)) becomes the exponent.
- What's inside the log function (\( 2x-1 \)) becomes the expression that the base is equated to once raised to the power.
Cube Root
Taking roots, especially cube roots, is a fundamental concept in math. In our example, we calculate \( 8^{\frac{1}{3}} \). This expression asks for the cube root of 8. So, what does this mean?
Essentially, finding the cube root of a number is determining the value that, when multiplied by itself three times, gives the original number.
Let's break it down:
Essentially, finding the cube root of a number is determining the value that, when multiplied by itself three times, gives the original number.
Let's break it down:
- The cube root of 8 is 2 because \(2 \times 2 \times 2 = 8\).
- When calculating roots, you are looking for a number that satisfies this multiplication condition.
- You often see roots written as fractional exponents, like \( \frac{1}{3} \) indicates a cube root.
Solving Equations
When solving equations, the goal is often to isolate the variable. This involves using a combination of algebraic techniques to find the value of \( x \). In our exercise, once simplified, our equation is \( 2 = 2x - 1 \). So how do we solve this?
Here's a step-by-step method for isolation:
Here's a step-by-step method for isolation:
- First, add 1 to both sides of the equation to remove the constant term from the side with \( x \), leading to \( 3 = 2x \).
- Second, divide both sides by 2, the coefficient of \( x \), to isolate \( x \).
- This results in \( x = 1.5 \).