Final answer:
A rational function is a function that can be written as a ratio or fraction of two polynomials. Option C, y = 2x, is a rational function as it is a linear function with polynomial terms.
Step-by-step explanation:
A rational function is a function that can be written as a ratio or fraction of two polynomials. To determine which of the given options is a rational function, we need to check if the function is in the form of f(x) = p(x)/q(x), where p(x) and q(x) are polynomials.
Looking at the options:
A) y = 5 − x/2 is not a rational function because it has a non-polynomial term in the numerator.
B) y = x² − x + 4 is not a rational function because it is a quadratic function with polynomial terms only.
C) y = 2x is a rational function because it is a linear function with polynomial terms.
D) y = (x − 3)/x² is a rational function because it is a fraction of two polynomials.
Therefore, the correct answer is option C, y = 2x.