Rational function

Rational function is a mathematical concept that plays a significant role in various branches of mathematics, including algebra, calculus, and complex analysis. A rational function is defined as the quotient of two polynomials. It is expressed in the form \(f(x) = \frac{P(x)}{Q(x)}\), where \(P(x)\) and \(Q(x)\) are polynomial functions of \(x\), and \(Q(x) \neq 0\). The domain of a rational function consists of all real numbers \(x\) except those for which the denominator \(Q(x) = 0\).

Definition

A rational function, \(f(x)\), can be defined as: \[f(x) = \frac{P(x)}{Q(x)}\] where:

• \(P(x)\) and \(Q(x)\) are polynomial functions of \(x\).
• \(Q(x) \neq 0\).

The highest degree of the polynomials \(P(x)\) or \(Q(x)\) determines the behavior and characteristics of the rational function.

Characteristics

Rational functions exhibit several important characteristics, including:

• Asymptotes: Vertical, horizontal, or oblique lines that the graph of the rational function approaches but never touches.
• Discontinuities: Points where the function is not defined, typically where \(Q(x) = 0\).
• End behavior: The behavior of the graph of the function as \(x\) approaches positive or negative infinity.

Types of Rational Functions

Rational functions can be categorized based on the degree of the numerator and denominator polynomials:

• Proper rational function: The degree of \(P(x)\) is less than the degree of \(Q(x)\).
• Improper rational function: The degree of \(P(x)\) is greater than or equal to the degree of \(Q(x)\). Improper rational functions can often be divided to produce a polynomial and a proper rational function.

Applications

Rational functions are used in various fields such as physics, engineering, economics, and biology to model relationships where one quantity varies inversely as another. Examples include the calculation of rates, optimization problems, and the analysis of systems' behavior.

Simplification and Operations

Rational functions can be simplified by factoring the numerator and the denominator and canceling out common factors. Operations such as addition, subtraction, multiplication, and division can be performed on rational functions, following the rules for fractions.

Graphing

The graph of a rational function can be complex, with features such as asymptotes and discontinuities. Understanding the function's algebraic properties can aid in sketching its graph.

See Also

• Polynomial
• Asymptote
• Discontinuity
• End behavior

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Rational function gallery

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  Rational Degree 3

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  Rational Degree 2 by Xedi