Chapter 2: Problem 55
Find the domain of the function. $$f(x)=\frac{3}{\sqrt{x-4}}$$
Short Answer
Expert verified
The domain of the function is \((4, \infty)\).
Step by step solution
01
Identify the Denominator
The given function is \( f(x)=rac{3}{ ext{expression}} \). Identify the denominator. Here, it is \( \sqrt{x-4} \).
02
Determine Valid Conditions for Roots
For \( \sqrt{x-4} \) to be a real number, the expression inside the square root must be non-negative. Therefore, set up the inequality: \( x-4 \geq 0 \).
03
Solve the Inequality
Solve the inequality \( x-4 \geq 0 \). Adding 4 to both sides, we get \( x \geq 4 \). This means that "\(x\)" can take any value greater than or equal to 4.
04
Evaluate Fraction Division
In a fraction, the denominator cannot be zero. Thus, \( \sqrt{x-4} eq 0 \). But since \( \sqrt{x-4} eq 0 \) translates to \( x eq 4 \), we already cover this with \( x \geq 4 \).
05
Combine Results
Considering \( x \geq 4 \) from Step 3 and the fraction condition that eliminates only \( x = 4 \), the domain is \( x > 4 \).
06
Express the Domain
Convert the domain condition into interval notation. Since \( x \) must be greater than 4, the domain in interval notation is \((4, \infty)\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Square Root Function
A square root function involves an expression that includes a square root. In our case, the function is \( f(x) = \frac{3}{\sqrt{x-4}} \). The presence of the square root \( \sqrt{x-4} \) indicates that we need to consider the domain of the function carefully. The expression inside the square root, \( x-4 \), must be non-negative because square roots of negative numbers are not real. Therefore, we set up the condition \( x-4 \geq 0 \). This inequality ensures the expression under the square root is at least zero, making it a real, non-negative number.
- Square roots only accept non-negative inputs.
- The expression inside the root dictates the constraints on \( x \).
Inequalities
Inequalities are mathematical expressions used to define a range of values. In this context, they help us identify where the function is defined. To find the domain of the function with a square root, we derive an inequality from the expression \( \sqrt{x-4} \). Specifically, we identify \( x-4 \geq 0 \). Solving this inequality requires simple algebra. When we add 4 to both sides, we get \( x \geq 4 \).
- Inequalities allow evaluation of conditions for mathematical expressions.
- Algebraic manipulation helps solve these inequalities.
Interval Notation
Interval notation is a format used to precisely describe a set of numbers, often concerning the domain of functions. Once the valid \( x \)-values are identified from inequalities, interval notation beautifully summarizes the range. In this example, we translate \( x > 4 \) into interval notation, rendering it as \((4, \infty)\).The parentheses \((4, \infty)\) indicate that 4 is not included, but any number greater than 4 is part of the domain. The \( \infty \) symbol is always accompanied by a parenthesis because infinity is a concept, not a tangible number you can "reach."
- Interval notation efficiently presents ranges.
- Parentheses or brackets show inclusion/exclusion of end points.