A polynomial function is a mathematical function defined by an expression that is a sum of terms, each of which is a product of a constant and a non-negative integer power of a variable. The term "polynomial" comes from the Greek word "polys," which means "many," and "nomos," which means "terms." Polynomial functions are distinguished by the degree of their highest-degree term, which is the largest exponent of the variable. For example, the polynomial function f(x) = x3 + 2x2 + x - 1 has a degree of 3 because the highest-degree term is x3.
Out of the four given options, only the functions f(x) = x3 + 2x2 + x - 1 and f(x) = x3 +1 are polynomial functions. The other two options, y = -2x3 + 5x – 4 - 4 and f(x) = V2x3 + 5, are not polynomial functions because they contain terms that are not of the form "constant times a non-negative integer power of a variable." The function y = -2x3 + 5x – 4 - 4 contains the term -4, which is not a product of a constant and a non-negative integer power of a variable, and the function f(x) = V2x3 + 5 contains the term V2x3, which is not a product of a constant and a non-negative integer power of a variable. Therefore, the correct answer is A and D.