Which is considered a real number?

A real number is defined as any value that can represent a distance along a number line. It includes both rational numbers (like integers and fractions) and irrational numbers (like the square root of non-perfect squares and pi).

Let's consider each option:

The number -5 is an integer and therefore a real number because it can easily be placed on the number line.

The expression √-1, however, is not a real number. The square root of a negative number is classified as an imaginary number. Since this does not fall within the definition of real numbers, it cannot be considered a valid choice.

The number π (pi) is an irrational number, which is also classified as a real number because it can be represented on the number line, despite its decimal representation being non-repeating and non-terminating.

Thus, the only numbers in the options that are classified as real numbers are -5 and π. While the answer provided highlights one of these real numbers, the presence of √-1 disqualifies any interpretation suggesting that all choices consist of real numbers. Thus, the correct assertion is that both -5 and π are real numbers, while √-1 is not, leading to the conclusion that the answer that encompasses only real