Symbol | Name | Explanation |

Q | rational numbers | When we divide an integer (a) by another integer (b) we get a rational number. Every rational number is represented by an integer part. For example, if a = 6 and b = 2, we get the rational number 3.0. If a = 1 and b = 2, we get the rational number 0.5. Both have a finite number of places after the comma and are called rationals of There are cases where the number of squares after the comma is infinite. For example, a = 1 and b = 3 gives us the rational number 0,33333… It's called We can assume that rational numbers encompass all integers and those that lie in the intervals between integers. Q = {a / b | The Remember that The symbol Q * = {x Q | x 0} The symbol Q + = {x Q | x 0} The symbol Q- = {x Q | x 0} The symbol Q * + = {x Q | x> 0} The symbol Q * - = {x Q | x <0} |

I | irrational numbers | These are real numbers that cannot be obtained by dividing two integers, that is, they are real numbers, but not rational. These numbers have infinite houses after the comma, which do not repeat periodically. The most famous irrational number is pi (). |

R | real numbers | The set of all rational and irrational numbers is the set of real numbers, indicated by R.We indicate by
The symbol R + = {x R | x 0} The symbol R- = {x R | x 0} The symbol R * + = {x R | x> 0} The symbol R * - = {x R | x <0} |

Ç | complex numbers | A complex number is represented by a + bi being The the real part and B the imaginary part.Imaginary unit: defines the imaginary unit, represented by the letter |

Comparation | It's smaller than, it's bigger than
| |

and | Comparation | is less than or equal to, is greater than or equal to xy means: x is less than or equal to y; |