Chapter 1: Problem 52
Find the (implied) domain of the function. $$f(x)=\frac{6}{4-\sqrt{6 x-2}}$$
Short Answer
Expert verified
The domain is \( x \in [\frac{1}{3}, 3) \cup (3, \infty) \)."
Step by step solution
01
Identify restrictions from the square root
The expression inside the square root, \( \sqrt{6x-2} \), requires that the expression \( 6x-2 \) must be greater than or equal to zero for real-valued outputs. Thus, set \( 6x-2 \geq 0 \) and solve for \( x \).
02
Solve inequality for x
Solve \( 6x-2 \geq 0 \) by adding 2 to both sides, resulting in \( 6x \geq 2 \). Then, divide by 6 to find \( x \geq \frac{1}{3} \).
03
Identify restrictions from the fraction
For the fraction to be defined, the denominator \( 4 - \sqrt{6x-2} \) cannot be zero. Thus, set \( 4 - \sqrt{6x-2} eq 0 \) and solve for \( x \).
04
Solve equation for equality
If \( 4 - \sqrt{6x-2} = 0 \), then \( \sqrt{6x-2} = 4 \). Square both sides to get \( 6x-2 = 16 \). Solve for \( x \) by adding 2 and then dividing by 6, resulting in \( x = 3 \). Thus, \( x eq 3 \).
05
Combine the inequalities
Combine the allowable values for \( x \) from both steps. From Step 1, \( x \geq \frac{1}{3} \) and from Step 2, \( x eq 3 \). The domain of \( f(x) \) is \( x \in [\frac{1}{3}, 3) \cup (3, \infty) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Inequalities
Understanding inequalities is crucial when finding the domain of a function. When dealing with functions, inequalities can help us determine the set of possible inputs (x-values) that will keep the function valid. For example, in expressions like \( 6x - 2 \geq 0 \), the inequality shows us the conditions under which the expression inside a square root remains non-negative. In this case, ensuring that \( x \geq \frac{1}{3} \) means only working with values of \( x \) that make the square root result in a real number.To solve an inequality, we approach it as a step-by-step process similar to solving regular equations, but with careful attention to the direction of the inequality sign. This often involves operations such as one-side additions, subtractions, or even multiplications and divisions, while ensuring the inequality holds through each step.
Square root restrictions
Square roots are only defined for non-negative numbers. This means that for any expression like \( \sqrt{6x - 2} \), the condition \( 6x - 2 \geq 0 \) must be met. If this condition is not satisfied, the square root will not yield a real number and hence be invalid in standard mathematical contexts used in schooling.To ensure the entire expression under the square root is non-negative, you can calculate the critical points using inequality. Solving \( 6x - 2 \geq 0 \) gives us values of \( x \) where the square root remains valid, which is essential when defining the domain of a function involving square roots. Thus, the rule of thumb is that the expression inside a square root must be zero or positive.
Fractional expressions
Fractional expressions introduce another layer of conditions when finding a function's domain. A critical requirement is ensuring the denominator never equals zero, as division by zero is undefined in mathematics. For the function in question, \( \frac{6}{4 - \sqrt{6x - 2}} \), we need to ensure that \( 4 - \sqrt{6x - 2} eq 0 \).If the denominator ends up equaling zero, this would make the expression undefined. For instance, we calculate \( \sqrt{6x - 2} = 4 \) to find the offending \( x \) that makes the denominator zero. Solving gives us \( x = 3 \), which tells us to exclude \( x = 3 \) from the domain. Such restrictions are typical in maintaining legitimacy and definition within the realm of real numbers.
Real-valued outputs
For a function to be real-valued, it must produce real numbers as outputs for every input in its domain. This is a fundamental requirement, especially in educational settings where complex numbers are yet to be introduced.In the context of our function, both the square root and fraction components impose conditions on \( x \) to ensure all results are real numbers. By solving the inequality \( 6x - 2 \geq 0 \) and checking \( 4 - \sqrt{6x-2} eq 0 \), we derive a domain where the function reliably calculates real values: \( x \in \left[ \frac{1}{3}, 3 \right) \cup (3, \infty) \). Separating the domain like this ensures that every permissible \( x \) yields a legitimate, sensible answer from the function.