In this explainer, we will learn how to perform mathematical operations on radicals and how to utilize the conjugate to rationalize the denominator of a radical and simplify radical expressions.

Before we start looking at how to simplify radical expressions, let us first clearly define what we mean when we talk about radicals and define some associated mathematical language.

Firstly, the word radical describes the “root sign”; the number contained within the root sign is called the radicand, and the little number on the outside of the radical is call the index which tells us if we are dealing with a square root, a cube root, or otherwise. These terms have been labeled in the following picture.

When we want to simplify radicals, we want to minimize the size of the radicand. In order to do this, we first need to introduce two key rules.

### Key Rules: Products and Quotients of Radicals

It is worth noting that, generally, when simplifying radicals, we tend to focus on square roots, though the methods can be applied to radicals of any index (provided simplification calculations only contain radicals with the same index).

In order to minimize the radicand, we need to use the reverse of rule one. Let us consider the radical expression .

The number 32 is a multiple of 16 which is a perfect square, so, we can rewrite as . If we then apply rule one in reverse, we can see that and, as 16 is a perfect square, we can simplify this to find that

You may notice that 32 is also a multiple of 4 which is another perfect square. We could then rewrite as which is the same as , which simplifies to . Here, however, we have not minimized the radicand as 8 is still a multiple of a perfect square. So, we can continue the process:

This simplifies to as before.

It is generally easiest to identify the largest perfect square that is a factor of the number you are simplifying and then the method will be more efficient. In case, however, you happen to start with a perfect square that is not the largest factor, it is always worth checking your resulting expression to see if it has any more perfect squares as factors (in other words, can the radicand be reduced further?).

Let us now look at a more formal example.

Express in the form where and are integers and takes the least possible value.

With these questions, it is often helpful to write out a list of perfect squares:

From this list, we can see that the largest perfect square that is a factor of 640 is 64. We can then rewrite the radical as follows:

Now, let us look at a second example where the radical is given in the from , but is a multiple of a perfect square.

Express in the form where and are integers and takes the least possible value.

Here, we need to rewrite the expression by simplifying the radical and then multiplying the result by 3:

Finally, let us look at couple of examples where the simplification of the radical is only part of the question.

### Example 3: Simplifying Expressions Containing Multiple Radicals

Express in its simplest form.

First, we need to look at each of the radicals separately and see if they can be simplified. We can see that can not be reduced further as 3 is prime. The , however, can be simplified as 4 is a factor of 12. So,

Now, if we look at we can see that this too simplifies further as it is a multiple of 25. So, we find that

So, the original expression is the same as

As we have three terms containing radicals of equal index, and equal radicand, we can simplify this expression to get .

### Example 4: Simplifying Expressions Containing Multiple Radicals

Express in its simplest form.