How Do You Know if a Circle Is Opened or Closed on a Number Line?

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You should be able to tell whether a circle is open or closed just by looking at the associated number line. Find out how you know if a circle is open or closed on a number line with help from a distinguished math teacher in this free video clip.

Part of the Video Series: Algebra Help
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Video Transcript

Hi my name is Marija. I'm a mathematician and today I'm going to tell you how you know if a circle is open or closed on a number line. So if you're given an inequality to graph such as X is greater than 3, then when you go to graph it I know that 3 is not part of my solution because this inequality says that X has to be greater than 3. So it can be 4, it can be 5, it can even be 3.1 or 3.2 but it can't be 3. So the way that I show on a graph that it cannot be 3 is by putting an open circle on 3 and then I just shade everything over to the right because everything over to the right of 3 is part of the solution. So because there's no or equal to sign in this inequality I have to put an open circle, but if I change it and I said X is greater than or equal to 3, now I can shade in my circle. So the line underneath is what indicates to me that I need to shade in that circle because now 3 is part of the solution. This says that X can be 3 or it can be any number greater than 3. So 3 is part of my solution and that's why I shade it in. So no line underneath, open circle, line underneath, shaded circle. My name is Marija and I just showed you how to tell whether it's an open circle or a closed circle on a number line.


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