Final answer:
A polynomial function can be expressed as a sum of non-negative integer powers of x with real number coefficients. Given the options, f(x)=x and r(x)=2x are the functions that fit within this definition, making them polynomial functions.
Step-by-step explanation:
To determine which of the given functions is a polynomial, we must first understand the definition of a polynomial function. A polynomial function is one that can be expressed in the form f(x) = anxn + an-1xn-1 + ... + a2x2 + a1x1 + a0, where n is a non-negative integer, and the coefficients an, an-1, ..., a1, a0 are real numbers.
Looking at our options:
- f(x) = x can be written as f(x) = 1x1 + 0, which fits the form of a polynomial function.
- g(x) = log2x is not a polynomial function, as it contains a logarithm.
- r(x) = 2x can also be expressed in polynomial form as r(x) = 2x1 + 0.
- s(x) = |x+2| is not a polynomial since the absolute value function is not allowed in polynomial expressions.
Therefore, both f(x) and r(x) are polynomial functions.