Final answer:
The domain of the function representing the number of batches of cookies baked as a function of cups of sugar added is all non-negative whole numbers or common fractions, limited by the recipe amounts.
Step-by-step explanation:
The student has asked about the domain of a function in the context of ninth-grade students baking cookies. In mathematics, the domain of a function refers to the set of all possible input values (in this case, the number of cups of sugar, x) that the function can accept. Because we're discussing a real-world scenario about baking cookies, the domain would be all non-negative real numbers because you cannot add a negative amount of sugar while baking. It would also be discrete since you cannot add a fraction of a granule of sugar; in practice, it is usually measured in whole or sometimes half cups. Therefore, the domain of the function f(x) which models the number of batches of cookies as a function of cups of sugar added would include all non-negative whole numbers or fractions commonly used in baking, up to the amount that the recipe allows