What is the formula for a rational function?

A rational function is defined as a function that can be expressed as the quotient of two polynomials. The standard form of a rational function can be written as ( f(x) = \frac{P(x)}{Q(x)} ), where ( P(x) ) and ( Q(x) ) are polynomial functions.

The selected answer captures the essence of rational functions in a format that emphasizes the relationship between the numerator (represented by ( a )) and the denominator (represented by ( b )). By reflecting this structure, it highlights that the function represents a ratio of two expressions, aligning with the definition of rational functions.

In contrast, the other choices do not represent the general form of a rational function. They either resemble linear functions or other forms of expressions that do not capture the division of two polynomial functions essential to defining rational functions. The formulation in the correct option accurately represents this crucial characteristic found in rational expressions.