Chapter 5: Problem 52
For what value of \(x\) is it true that \((\log x)^{3}=3 \log x ?\)
Short Answer
Expert verified
The values of \(x\) are \(1\), \(10^{\sqrt{3}}\), and \(10^{-\sqrt{3}}\).
Step by step solution
01
Understand the Equation
We have the equation \((\log x)^3 = 3 \log x\). Our goal is to find the value of \(x\) that satisfies this equation. We need to consider possible solutions, including trivial cases like \(\log x = 0\).
02
Analyze the Potential Solutions
Rearrange the equation by letting \(y = \log x\). The equation becomes \(y^3 = 3y\). At this stage, we can attempt to factorize this equation.
03
Factor the Equation
Factoring \(y^3 = 3y\), we get \(y(y^2 - 3) = 0\). This gives us possible solutions: \(y = 0\) or \(y^2 - 3 = 0\).
04
Solve for \(y\)
First, solve \(y = 0\): Here, \(\log x = 0\), which means \(x = 10^0 = 1\). Then solve \(y^2 - 3 = 0\): \(y = \pm\sqrt{3}\).
05
Determine the Values of \(x\) from \(y\)
If \(y = \log x = \sqrt{3}\), then \(x = 10^{\sqrt{3}}\). If \(y = \log x = -\sqrt{3}\), then \(x = 10^{-\sqrt{3}}\).
06
Verify Solutions
Double-check if \(x = 1\), \(x = 10^{\sqrt{3}}\), and \(x = 10^{-\sqrt{3}}\) satisfy the original equation. They do, as substituting them back validates \((\log x)^3 = 3 \log x\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Factoring Equations
Factoring equations is a fundamental technique in algebra that involves expressing a polynomial or mathematical expression as a product of its factors. When given an equation like \( y^3 = 3y \), our goal is to simplify and solve it by finding the values for \( y \). In this case, we notice that each term in the equation has a common factor. By factoring, we rewrite this as:
- \( y(y^2 - 3) = 0 \)
Solving for Unknowns
Once an equation is factored, the next step is to solve for the unknowns involved. When we have \( y(y^2 - 3) = 0 \), it implies two potential solutions:
- \( y = 0 \) leads to \( \log x = 0 \), and since \( 10^0 = 1 \), we find \( x = 1 \).
- \( y^2 - 3 = 0 \) can be solved by adding 3 to both sides and taking the square root, yielding \( y = \pm\sqrt{3} \).
Properties of Logarithms
Logarithms are an essential concept in mathematics used to represent and solve exponential equations. The core property that we use here is that \( \log_{10}(x) = y \) means \( x = 10^y \), which helps us convert between logarithmic and exponential forms.
- For \( y = 0 \), we know \( x = 10^0 = 1 \).
- For \( y = \sqrt{3} \), we find \( x = 10^{\sqrt{3}} \).
- For \( y = -\sqrt{3} \), it translates to \( x = 10^{-\sqrt{3}} \).