# Category: Irrational Numbers

## Squares and Square Roots

To square a number, multiply it by itself.

For, example, square of $5$ is ${5}\times{5}={25}$.

When we talked about exponents and integers, we said that number $a$ raised to $b$-th power is number $a$ multiplied by itself $b$ times: $\color{purple}{a^b=\underbrace{a\cdot a\cdot a\cdot a\cdot...\cdot a}_{b}}$.

## Perfect Square

Perfect square is a result of multiplying a whole number by itself.

Whole number 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Perfect square (square of a whole number) 0 1 4 9 16 25 36 49 64 81 100 121 144 169 196 225

Perfect numbers are written on the main diagonal of the multiplication table.

## Cubes and Cube Roots

To cube a number, use it in multiplication three times.

For, example, cube of $5$ is ${5}\times{5}\times{5}={125}$.

When we talked about exponents and integers, we said that the number $a$ raised to $b$-th power is the number $a$ multiplied by itself $b$ times: $\color{purple}{a^b=\underbrace{a\cdot a\cdot a\cdot a\cdot...\cdot a}_{b}}$.

## Perfect Cube

Perfect cube is a result of cubing a whole number by itself.

Whole number 0 1 2 3 4 5 6 7 8 9 10 Perfect cube (cube of a whole number) 0 1 8 27 64 125 216 343 512 729 1000

## Nth Root

Similarly to square root and cube root, we can define nth root.

Nth root of a number $b$ is such number $a$, that $a^n=b$.

Notation for the nth root is the following: $\color{purple}{\sqrt[n]{b}}$.

## What is Irrational Number

Irrational number is a number, that is not rational.

What does that mean?

It means, that we can't represent irrational number as a fraction, decimal with finite number of digits, or repeating decimal.

## Irrational Numbers on a Number Line

Since each irrational number can be represented as infinite decimal, then we can proceed in the same way, as we did when placed decimals on a number line.

$\pi\approx{3.14}$, so it is slightly to the right of 3.

## Real Numbers

Real numbers are rational numbers plus irrational numbers.

Since rational numbers include integers and fractions, then real numbers include:

• integers {..., -5,-4,-3,-2,-1,0,1,2,3,4,5,...}
• fractions (proper, improper, mixed numbers)
• irrational numbers (like $\sqrt{{{2}}}$, ${\sqrt[{{3}}]{{-{15}}}}$, $\pi$, ${e}$ etc.)

A set of real numbers, i.e. a group of real numbers, is denoted by $\mathbb{R}$.