/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 42 Solve each logarithmic equation.... [FREE SOLUTION] | 91Ó°ÊÓ

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Solve each logarithmic equation. Express all solutions in exact form. Support your solutions by using a calculator. $$\log _{7}\left(x^{3}+65\right)=0$$

Short Answer

Expert verified
The solution is \( x = -4 \).

Step by step solution

01

Understand the Logarithmic Equation

The equation is given as \( \log_{7}(x^3 + 65) = 0 \). This means that the logarithm base 7 of \( x^3 + 65 \) is equal to 0.
02

Rewrite in Exponential Form

Using the property of logarithms, \( \log_b(y) = 0 \) implies \( y = b^0 \). Therefore, rewrite the equation as \( x^3 + 65 = 7^0 \). Since \( 7^0 = 1 \), it simplifies to \( x^3 + 65 = 1 \).
03

Solve for \( x^3 \)

Isolate \( x^3 \) by subtracting 65 from both sides of the equation: \( x^3 = 1 - 65 \). This gives \( x^3 = -64 \).
04

Solve for \( x \)

To find \( x \), take the cube root of both sides: \( x = \sqrt[3]{-64} \). Since \( -64 = (-4)^3 \), the solution is \( x = -4 \).
05

Verify the Solution with a Calculator

Substitute \( x = -4 \) back into the original equation to verify. Calculate \( x^3 + 65 \) as follows: \( (-4)^3 + 65 = -64 + 65 = 1 \). Check using the logarithm: \( \log_{7}(1) = 0 \) which confirms the solution is correct.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Exponential Form
When dealing with logarithmic equations, converting them into exponential form is often a helpful method. The basic relationship between logarithms and exponents is essential: if you have an equation in the form of \( \log_b(y) = x \), then it can be rewritten as \( b^x = y \). This conversion is a key strategy in solving logarithmic equations, as it enables us to remove the logarithm by expressing it in terms of an exponent.
In the given problem, we were initially presented with the equation \( \log_{7}(x^3 + 65) = 0 \). By rewriting it into exponential form, we use the relationship \( y = b^0 \) because any number raised to the power of 0 is 1. Thus, the equation becomes \( x^3 + 65 = 7^0 \) which simplifies to \( x^3 + 65 = 1 \). This simplification helps in easily isolating other components in the equation, allowing us to solve for \( x^3 \) first.
Understanding how to manipulate these forms and the ease with which exponential equations can be solved compared to log equations is powerful. It reduces complex expressions into more straightforward arithmetic calculations.
Cube Root
Taking the cube root is an essential algebraic operation, particularly when dealing with problems involving cubic equations. When asking for the cube root of a number, we are essentially seeking a value that, when multiplied by itself twice more, equals the original number.
In the exponential form derived from the logarithmic problem, we had the equation \( x^3 = -64 \). The next logical step was to find the cube root on both sides to solve for \( x \). Calculating \( \sqrt[3]{-64} \) gives \( x = -4 \), because \( (-4)^3 = -64 \). It's crucial to remember that cube roots, unlike square roots, retain the sign of the number, allowing for real-number solutions in cases where the radicand (number under the root symbol) is negative.
  • Cube roots can yield negative results when the original number is negative.
  • This property makes them particularly useful in equations involving negative numbers.
  • Always verify by cubing the result to ensure accuracy.
Understanding this operation is useful in both mathematics and practical scenarios that involve solving cubic relationships.
Base of Logarithm
The base of a logarithm is a fundamental aspect determining its behavior. A logarithm with a specific base describes how many times the base needs to be multiplied by itself to achieve a certain number. For example, \( \log_7(49) = 2 \) because \( 7^2 = 49 \).
In the original exercise, the logarithm had a base of 7. Understanding this concept helps in converting the logarithmic equation into exponential form. Choosing the correct base makes it possible to accurately perform calculations and comprehend the relationships between numbers.
  • The base indicates the repeated factor in the exponential form.
  • Common bases include 10 and \( e \) for common and natural logarithms, respectively.
  • As in the exercise, identifying the right base is crucial for correct conversions and operations.
Developing an understanding of logarithms with various bases enhances problem-solving abilities, as different bases can simplify different types of problems. It is important to recognize and apply the concept of the base when working with logarithmic and exponential equations, ensuring solutions are both accurate and efficient.

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Most popular questions from this chapter

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