What Is a Radical Sign?

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A radical sign, which looks like a check mark with a roof, is used to indicate what number multiplied by itself a certain number of times will give the final answer. Calculate the square root or cubed root of a number with a radical sign using help from a math teacher in this free video math lesson.

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Video Transcript

What is a radical sign? Seems kind of intimidating doesn't it? Hi, I'm Jimmy, I've been teaching math for nine years and I want to give you a little bit of an overview as to what radical signs are. Now, at first when you first see a radical sign, it might be intimidating but once you see what they do they can be easy to manage depending on the situation. Now, a radical sign is anything of this particular structure. It's kind of like a little check mark followed by like a roof over what's supposed to be a number or a variable here. Now, there's generally a number inside, but if you don't see a number here it's generally, it's always considered to be a square root. Now, if it's not a square root they have to put a number on the inside. So for example, three means there's a cube root. If you have a four on the outside, that means it's a fourth root. And the pattern continues. But what does it all mean? What do all those roots actually stand for? Well, they work with numbers or variables. Now here's and example as to square roots. With a square root, suppose you have square root of nine. What you have to ask yourself is, what number squared gives me nine on the inside. In other words what number multiplied by itself twice gives your nine. Well, that obviously is going to be three. The squared of nine is three. On the other hand, when you have the squared of seventeen, what number multiplied by itself twice gives you seventeen? Well, no number matches that description, so you have to leave it as it is. The best thing you can do is have a calculator and it'll give you and approximate value. But that's about it. Same thing with cube roots. Suppose you want to find out what the cubit of twenty seven is. That means what number multiplied by itself three times is going to give you twenty seven? Well after a little bit of head work you'll find out that that number happens to be three. What about the cubit of eight? In other words, what number multiplied by itself three times is going to give me the number eight? Well you find out that's going to give you two. But not every number works out like that. But that's the whole idea behind radical signs. They give you an indicator as to what number that multiplied by itself a certain number of times, which is what the radical sign indicates, is going to give you the final answer. So, I'm Jimmy and this has been an overview of radical signs.


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