Not using the correct logarithmic properties

Oct 13, 2025 by wbrum.org 58 views

Introduction

Logarithmic equations are a fundamental concept in mathematics, and solving them requires a deep understanding of the properties of logarithms. In this article, we will focus on solving two logarithmic equations, where the values of certain variables are missing. We will use the properties of logarithms to fill in the missing values and make the equations true.

Logarithmic Properties

Before we dive into the solutions, let's review some essential logarithmic properties:

Product Property: $\log_b (xy) = \log_b x + \log_b y$
Quotient Property: $\log_b \left(\frac{x}{y}\right) = \log_b x - \log_b y$
Power Property: $\log_b x^y = y \log_b x$
Change of Base Property: $\log_b x = \frac{\log_c x}{\log_c b}$

Solving Equation (b)

Let's start with equation (b): $\log_7 9 + \log_7 \square = \log_7 45$ . Our goal is to find the value of $\square$ .

Step 1: Use the Product Property

We can use the product property to rewrite the left-hand side of the equation:

$\log_7 9 + \log_7 \square = \log_7 (9 \square)$

Step 2: Equate the Expressions

Now, we can equate the expressions on both sides of the equation:

$\log_7 (9 \square) = \log_7 45$

Step 3: Use the One-to-One Property

Since the logarithmic function is one-to-one, we can drop the logarithms and equate the expressions inside:

$9 \square = 45$

Step 4: Solve for $\square$

Now, we can solve for $\square$ by dividing both sides of the equation by 9:

$\square = \frac{45}{9}$

$\square = 5$

Therefore, the value of $\square$ is 5.

Solving Equation (c)

Now, let's move on to equation (c): $\log_6 25 = \square \log_6 5$ . Our goal is to find the value of $\square$ .

Step 1: Use the Power Property

We can use the power property to rewrite the left-hand side of the equation:

$\log_6 25 = \log_6 5^2$

Step 2: Use the Power Property Again

Now, we can use the power property again to rewrite the expression:

$\log_6 5^2 = 2 \log_6 5$

Step 3: Equate the Expressions

Now, we can equate the expressions on both sides of the equation:

$2 \log_6 5 = \square \log_6 5$

Step 4: Solve for $\square$

Now, we can solve for $\square$ by dividing both sides of the equation by $\log_6 5$ :

$\square = \frac{2 \log_6 5}{\log_6 5}$

$\square = 2$

Therefore, the value of $\square$ is 2.

Conclusion

In this article, we solved two logarithmic equations, where the values of certain variables were missing. We used the properties of logarithms to fill in the missing values and make the equations true. By following the steps outlined in this article, you should be able to solve similar logarithmic equations on your own.

Common Mistakes to Avoid

When solving logarithmic equations, it's essential to avoid common mistakes. Here are a few to watch out for:

Not using the correct logarithmic properties: Make sure to use the correct properties of logarithms, such as the product property, quotient property, power property, and change of base property.
Not equating the expressions correctly: When equating the expressions on both sides of the equation, make sure to use the correct equality sign.
Not solving for the correct variable: Make sure to solve for the correct variable, and not for a different variable that is not present in the equation.

Practice Problems

To practice solving logarithmic equations, try the following problems:

$\log_8 27 + \log_8 \square = \log_8 81$
$\log_9 16 = \square \log_9 2$

Introduction

Logarithmic equations can be challenging to solve, but with the right approach and practice, you can become proficient in solving them. In this article, we will answer some common questions about logarithmic equations, providing you with a deeper understanding of the subject.

Q: What is a logarithmic equation?

A: A logarithmic equation is an equation that involves a logarithmic function. It is an equation that can be written in the form $\log_b x = y$ , where $b$ is the base of the logarithm, $x$ is the argument of the logarithm, and $y$ is the result of the logarithm.

Q: What are the common properties of logarithms?

A: There are four common properties of logarithms:

Product Property: $\log_b (xy) = \log_b x + \log_b y$
Quotient Property: $\log_b \left(\frac{x}{y}\right) = \log_b x - \log_b y$
Power Property: $\log_b x^y = y \log_b x$
Change of Base Property: $\log_b x = \frac{\log_c x}{\log_c b}$

Q: How do I solve a logarithmic equation?

A: To solve a logarithmic equation, you need to follow these steps:

Use the correct logarithmic property: Choose the correct property of logarithms to apply to the equation.
Simplify the equation: Simplify the equation by applying the chosen property.
Equate the expressions: Equate the expressions on both sides of the equation.
Solve for the variable: Solve for the variable by isolating it on one side of the equation.

Q: What is the difference between a logarithmic equation and an exponential equation?

A: A logarithmic equation and an exponential equation are related but distinct concepts. A logarithmic equation is an equation that involves a logarithmic function, while an exponential equation is an equation that involves an exponential function. For example:

Logarithmic equation: $\log_2 x = 3$
Exponential equation: $2^3 = x$

Q: Can I use a calculator to solve logarithmic equations?

A: Yes, you can use a calculator to solve logarithmic equations. However, it's essential to understand the underlying mathematics and to use the calculator as a tool to verify your work.

Q: What are some common mistakes to avoid when solving logarithmic equations?

A: Some common mistakes to avoid when solving logarithmic equations include:

Not using the correct logarithmic property: Make sure to use the correct property of logarithms to apply to the equation.
Not equating the expressions correctly: When equating the expressions on both sides of the equation, make sure to use the correct equality sign.
Not solving for the correct variable: Make sure to solve for the correct variable, and not for a different variable that is not present in the equation.

Q: How can I practice solving logarithmic equations?

A: You can practice solving logarithmic equations by:

Solving problems: Try solving problems from a textbook or online resource.
Using online resources: Use online resources, such as Khan Academy or Mathway, to practice solving logarithmic equations.
Working with a tutor: Work with a tutor or teacher to practice solving logarithmic equations.

Conclusion

Logarithmic equations can be challenging to solve, but with practice and the right approach, you can become proficient in solving them. By following the steps outlined in this article and practicing regularly, you can develop a deeper understanding of logarithmic equations and become more confident in your ability to solve them.