Question

pls help (will give brainliest if possible!)

Answer 1

The real number √21 is an example of an irrational number. (Correct choice: C)

What number is real and irrational?

According to number theory, real numbers are formed by the following sets:

1. Natural numbers - Set of real numbers defined by N = {1, 2, 3, 4, 5, 6, ...}.
2. Whole numbers - Set of real numbers defined by the union of the set of natural numbers and the number 0.
3. Integers - Set of real numbers defined by the union of the set of whole numbers and Z = {- 1, - 2, - 3, - 4, - 5, - 6, ...}
4. Rational numbers - Set of real numbers defined by numbers of the form m / n, where m and n are integers and n is not zero. All integers are also rational numbers, but not all rational numbers are integers.
5. Irrational numbers - Set of real numbers that are not rational. All rational numbers can have an irrational representation, but not all irrational numbers are rational.

Then, by direct inspection we get the following conclusions:

• The real number 5.85858585... is a rational number.
• The real number 63.4 is a rational number (317 / 50).
• The real number √21 is an irrational number.
• The real number √36 is a rational number (6).

To learn more on irrational numbers: https://brainly.com/question/17450097

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