Chapter 3: Problem 6
In Exercises \(1-8,\) find the domain of each rational function. $$h(x)=\frac{x+8}{x^{2}-64}$$
Short Answer
Expert verified
The domain of the function \(h(x)=\frac{x+8}{x^{2}-64}\) is all real numbers except -8 and 8.
Step by step solution
01
Identify the Denominator
The denominator of the function is \(x^{2}-64\).
02
Find when the Denominator Equals Zero
To find the values of x that we must exclude from the domain, we set the denominator equal to zero and solve for x. \(x^{2} -64 = 0\), this is a difference of squares which can be expressed as \((x-8)(x+8) = 0\). Therefore, \(x = -8\) or \(x = 8\).
03
Express the Domain
The domain of the function is all real numbers except for the numbers that make the denominator zero. These numbers are \(x = -8\) and \(x = 8\). Thus, the domain of \(h(x)\) is all real numbers except -8 and 8.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Rational Functions
Rational functions are a type of function expressed as the quotient of two polynomials. This can be visualized as a fraction where the numerator and the denominator are both polynomial expressions. A typical rational function looks like this:
- Numerator: a polynomial, e.g. \( x + 8 \)
- Denominator: another polynomial, e.g. \( x^2 - 64 \)
Denominator Zero
A fundamental characteristic of rational functions is the restriction on values where the denominator equals zero. In mathematics, division by zero is undefined, which means any x-values that turn the denominator into zero must be excluded from the domain.To find these values, you set the denominator equal to zero and solve for \( x \).
- The equation \( x^2 - 64 = 0 \) determines these x-values.
- Simplifying the equation helps identify the critical points: \( (x - 8)(x + 8) = 0 \).
Difference of Squares
The concept of difference of squares is a special type of polynomial factoring which is very useful when working with rational functions. For instance, the expression \( x^2 - 64 \) can be factored because it is a difference of squares. This means it takes the form:\[ a^2 - b^2 = (a - b)(a + b) \]In the equation \( x^2 - 64 \), consider it as \( x^2 - 8^2 \), enabling factoring into \((x-8)(x+8)\).
- This factoring helps identify the points where the denominator becomes zero by setting each factor equal to zero.
- Solving these gives \( x = 8 \) and \( x = -8 \), which need to be excluded from the domain.
Real Numbers Exclusion
When we discuss the domain of a rational function, we typically mean the range of real numbers allowed as inputs. However, as we've seen, certain values must be excluded due to division by zero.Once determined that \( x = 8 \) and \( x = -8 \) make the denominator zero, these values are excluded from the domain. Thus, the domain of \( h(x) = \frac{x+8}{x^2-64} \) includes all real numbers except these two.
- To express the domain in interval notation, note that the function is defined from: \(( -\infty, -8 ) \cup (-8, 8) \cup (8, \infty)\).