Correct Answer: C

Rationale: The number -4 is classified as a real number because it exists on the number line. It is also a rational number since it can be expressed as -4/1. Additionally, -4 is an integer because it is a whole number that can be positive, negative, or zero. However, -4 is not a whole number because whole numbers are non-negative integers starting from zero. Similarly, -4 is not a natural number since natural numbers are positive integers starting from one. Therefore, the correct classification for the number -4 is real, rational, and integer, making option C the correct answer.

Correct Answer: D

Rationale: Xavier gives away half of his 20 apples (10), then gives 6 more apples, leaving him with 4 apples. He uses 3/4 of the remaining 4 apples (3) for the pie, leaving him with 1 apple at the end of the day. Therefore, the correct answer is 1. Choices A, B, and C are incorrect because they do not accurately reflect the calculations of apples given away and used for the pie, resulting in the remaining amount of 1 apple.

Correct Answer: D

Rationale: The factors of 12 are numbers that divide evenly into 12 without leaving a remainder. The correct factors of 12 are 1, 2, 3, 4, 6, and 12. Choice A (12, 24, 36) is incorrect as only 12 is a factor of 12. Choice B (1, 2, 4, 6, 12) includes all the correct factors of 12. Choice C (12, 24, 36, 48) is incorrect as 24, 36, and 48 are not factors of 12.

Correct Answer: C

Rationale: An equation represents a function if each input (x-value) corresponds to exactly one output (y-value). In the equation x = y^2, for a single x-value, there are two possible y-values (positive and negative square root), violating the definition of a function. This violates the vertical line test, where a vertical line intersects the graph in more than one point for non-functions. Choices A, B, and D all pass the vertical line test and represent functions, making them incorrect answers.

Correct Answer: A

Rationale: The domain of a function consists of all possible input values that produce a valid output. In the case of y = 1/x, the function is undefined when x = 0 because division by zero is not defined in mathematics. Therefore, the correct domain for y = 1/x is all real numbers except 0 (Choice A). Choice B, x > 0, is incorrect because it excludes the value x = 0. Choice C, x = 0, is also incorrect as x = 0 is not a valid part of the domain due to the function being undefined at this point. Choice D, x = 1, is unrelated to the domain of the function and does not represent the set of valid input values for y = 1/x.