Lesson Explainer: Simplifying Radicals | Nagwa Lesson Explainer: Simplifying Radicals | Nagwa

Lesson Explainer: Simplifying Radicals Mathematics

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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

  1. 𝑎×𝑏=𝑎𝑏
  2. 𝑎𝑏=𝑎𝑏

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 32.

The number 32 is a multiple of 16 which is a perfect square, so, we can rewrite 32 as 16×2. If we then apply rule one in reverse, we can see that 32=16×2, and, as 16 is a perfect square, we can simplify this to find that 32=42.

You may notice that 32 is also a multiple of 4 which is another perfect square. We could then rewrite 32 as 4×8 which is the same as 4×8, which simplifies to 28. Here, however, we have not minimized the radicand as 8 is still a multiple of a perfect square. So, we can continue the process: 2×8=2×4×2.

This simplifies to 2×2×2=42, 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.

Example 1: Simplifying Radicals

Express 640 in the form 𝑎𝑏 where 𝑎 and 𝑏 are integers and 𝑏 takes the least possible value.

Answer

With these questions, it is often helpful to write out a list of perfect squares: 1,4,9,16,25,36,49,64,81,100,121,144,.

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: 640=64×10=64×10=810.

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

Example 2: Simplifying Radicals

Express 345 in the form 𝑎𝑏 where 𝑎 and 𝑏 are integers and 𝑏 takes the least possible value.

Answer

Here, we need to rewrite the expression by simplifying the radical 45 and then multiplying the result by 3: 345=3×9×5=3×9×5=3×3×5=95.

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 3+1275 in its simplest form.

Answer

First, we need to look at each of the radicals separately and see if they can be simplified. We can see that 3 can not be reduced further as 3 is prime. The 12, however, can be simplified as 4 is a factor of 12. So, 12=4×3=4×3=23.

Now, if we look at 75 we can see that this too simplifies further as it is a multiple of 25. So, we find that 75=25×3=25×3=53.

So, the original expression is the same as 3+2353.

As we have three terms containing radicals of equal index, and equal radicand, we can simplify this expression to get 23.

Example 4: Simplifying Expressions Containing Multiple Radicals

Express 75+2827 in its simplest form.

Answer

To solve this question, we need to consider each of the radicals individually and see if they can be simplified. First, we have 75 which can be simplified as 28 is a multiple of 25: 75=25×3=25×3=53.

Secondly, we have 28 which can be simplified as: 28=4×7=4×7=27.

Finally, 27 can be simplified as 27 is a multiple of 9: 27=9×3=9×3=33.

We can, therefore, rewrite the expression as 53+2733, and we can combine the first and last terms, as they contain the same radicand, to get 23+27.

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