The Importance of Domain and Range

Oct 13, 2025 by wbrum.org 3 views

Understanding the Domain and Range of a Rational Function

In mathematics, a rational function is a function that can be expressed as the ratio of two polynomials. The domain of a rational function is the set of all possible input values (x-values) for which the function is defined, while the range is the set of all possible output values (y-values) that the function can produce. In this article, we will explore the domain and range of a given rational function, $f(x)=\frac{2 x^2+5 x-12}{x+4}$ .

The Importance of Domain and Range

The domain and range of a function are crucial in understanding its behavior and properties. The domain tells us the possible input values for which the function is defined, while the range tells us the possible output values that the function can produce. In the case of a rational function, the domain and range can be affected by factors such as division by zero, which can lead to undefined or infinite values.

Finding the Domain of a Rational Function

To find the domain of a rational function, we need to identify the values of x that make the denominator equal to zero. In the case of the given rational function, $f(x)=\frac{2 x^2+5 x-12}{x+4}$ , the denominator is $x+4$ . We can set the denominator equal to zero and solve for x to find the values that make the function undefined.

$x+4=0$

$x=-4$

Therefore, the domain of the function is all real numbers except $x=-4$ . We can write this as:

$D:\{x \in \mathbb{R} \mid x \neq -4\}$

Finding the Range of a Rational Function

To find the range of a rational function, we need to consider the possible output values of the function. In the case of the given rational function, $f(x)=\frac{2 x^2+5 x-12}{x+4}$ , we can start by factoring the numerator to simplify the expression.

$2 x^2+5 x-12 = (2 x-3)(x+4)$

Now, we can rewrite the function as:

$f(x)=\frac{(2 x-3)(x+4)}{x+4}$

We can cancel out the common factor of $x+4$ in the numerator and denominator, leaving us with:

$f(x)=2 x-3$

This simplified expression tells us that the function is a linear function with a slope of 2 and a y-intercept of -3. Since the function is linear, its range is all real numbers. However, we need to consider the value of x that makes the original function undefined, which is $x=-4$ . When $x=-4$ , the function is undefined, and the corresponding output value is also undefined. Therefore, the range of the function is all real numbers except $y=-11$ .

$R:\{y \in \mathbb{R} \mid y \neq -11\}$

Conclusion

In conclusion, the domain and range of a rational function are crucial in understanding its behavior and properties. By identifying the values of x that make the denominator equal to zero, we can find the domain of the function. By considering the possible output values of the function, we can find the range. In the case of the given rational function, $f(x)=\frac{2 x^2+5 x-12}{x+4}$ , the domain is all real numbers except $x=-4$ , and the range is all real numbers except $y=-11$ .

Final Answer

The final answer is:

A. $D:\{x \in \mathbb{R} \mid x \neq -4\}, \ R:\{y \in \mathbb{R} \mid y \neq -11\}$