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Square Roots

Learning text on the topic Square Roots

Square Roots – Definition

Square roots are a fundamental concept in mathematics, especially in algebra and geometry. They are used in various real-life scenarios, such as calculating the area of land, determining the size of a television screen, or in architectural designs.

The square root of a number is a value that, when multiplied by itself, gives the original number. For example, the square root of $9$ is $3$ because $3 \times 3$ equals $9$.

The Square Root Symbol

There are two important terms to remember when you’re dealing with square roots. They are the radical sign and the radicand.

  • The radical sign: The radical sign, denoted as $\sqrt{}$, is a symbol used in mathematics to indicate the square root of a number or expression placed within it. This sign is essential in operations involving square roots.

  • The radicand: The radicand is the number or expression inside the radical sign. It is the value for which the square root is being calculated. For example, in $\sqrt{25}$, the radicand is $25$.


Understanding Square Roots

The concept of square roots is crucial for working with the Pythagorean theorem, understanding geometric shapes, and dealing with powers and exponents.

The following concepts are helpful when dealing with square roots:

  • Perfect squares: Numbers like $9$, $16$, or $25$ are perfect squares because they can be expressed as the square of an integer.
  • Irrational numbers: Square roots of non-perfect squares, like $\sqrt{2}$ or $\sqrt{17}$, are irrational numbers. They cannot be expressed as a simple fraction and have non-repeating, non-terminating decimal representations. Here is some more information on these Types of Numbers amongst others!
  • Positive and negative roots: Every positive number has two square roots - a positive and a negative root. For instance, both $+3$ and $-3$ are square roots of $9$.

Perfect Squares – Chart

The table below shows an overview of common perfect squares:

Square Root and Solution Proof
$ \sqrt{1} = 1 $ $ 1^2 = 1 $
$ \sqrt{4} = 2 $ $ 2^2 = 4 $
$ \sqrt{9} = 3 $ $ 3^2 = 9 $
$ \sqrt{16} = 4 $ $ 4^2 = 16 $
$ \sqrt{25} = 5 $ $ 5^2 = 25 $
$ \sqrt{36} = 6 $ $ 6^2 = 36 $
$ \sqrt{49} = 7 $ $ 7^2 = 49 $
$ \sqrt{64} = 8 $ $ 8^2 = 64 $
$ \sqrt{81} = 9 $ $ 9^2 = 81 $
$ \sqrt{100} = 10 $ $ 10^2 = 100 $
$ \sqrt{121} = 11 $ $ 11^2 = 121 $
$ \sqrt{144} = 12 $ $ 12^2 = 144 $

It is helpful to memorize the perfect squares up until at least $12^2=144$, especially when you progress to more challenging concepts like simplifying radical expressions.

Square Roots – Guided Practice

Let’s work through the following question together: Find the square root of $49$.

What number, when multiplied by itself, equals $49$?
Is there another square root for $49$?
So, what are the square roots of $49$?

Calculating Square Roots Using Prime Factorization

When you're finding the square root of a number, especially a large one, prime factorization is a useful tool. This method involves breaking down a number into its prime factors – the prime numbers that multiply together to make the original number. Once you have the prime factors, you can easily find the square root, especially for perfect squares.

Step Description
1 Create a factor tree: Start by making a factor tree to break down the number into its prime factors.
2 Identify prime factors: Once you've completed the factor tree, list out all the prime factors you've found.
3 Group into pairs: Arrange the prime factors into pairs. If there’s an unpaired factor, the number is not a perfect square.
4 Multiply for square root: Multiply one factor from each pair to find the square root of the original number.


  • The prime factors of $144$ are $2 \cdot 2 \cdot 2 \cdot 2 \cdot 3 \cdot 3$.
  • These can be paired into three total groups: $2 \cdot 2 \cdot 3$.
  • $2 \cdot 2 \cdot 3 = 12$ so the square root of $144$ is $12$.

Square Roots – Exercises

Here are some more exercises on square roots. Find the answer to the question and click on the question box to reveal the correct answer.

Square Roots – Real-World Problems

Let’s take a look at some real-world examples including square roots.


In the video game scenario, why can't the solution to the length of the square door be $-14$ ft?

Square Roots – Summary

Let’s review what we’ve learned about square roots in this text:

Key Learnings from this Text:

  • Square roots help find a number that, when squared, gives the original number.
  • Square roots of perfect squares are integers, while those of non-perfect squares are irrational.
  • Every positive number has two square roots: one positive and one negative.
  • The radical sign, denoted as $\sqrt{ }$, is a symbol used in mathematics to indicate the square root of a number or expression placed within it.
  • The radicand is the number or expression inside the radical sign.

Understanding Square roots can come in handy when you learn more about the Pythagorean theorem.

Square Roots – Frequently Asked Questions

What is a square root?
What are perfect squares?
Can negative numbers have square roots?
How do you find the square root of a number?
Are square roots always rational numbers?
What is the square root of a number like $2$?
Why are there two square roots for a positive number?
Is the square root of $0$ also $0$?
How are square roots used in real life?
Can square roots be used to solve equations?

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