Question Video: Writing a Set Given in the Descriptive Form Using the Listing Method Mathematics

𝑋 is the set of odd numbers greater than 8. Write 𝑋 using the listing method.

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Video Transcript

𝑋 is the set of odd numbers greater than eight. Write 𝑋 using the listing method.

Well, in this question, if we want to list our set and find each of the elements, then what we’re gonna need to do is take a look at these two key bits of information. We want the set to be odd numbers, but they must be greater than eight. Well, we’ve got one problem. The odd numbers greater than eight is gonna be a lot of numbers. In fact, it’s gonna be ∞ numbers. So our set is gonna have ∞ elements because it’ll keep going on and on and on. So what are we gonna do?

Well, first of all, what we’re gonna do is list our first value because the first odd number that’s greater than eight is nine. And then, what we’re gonna do is list a couple more values, 11 and 13. But then, instead of having to list lots and lots and lots of different values or lots of different elements, all we do is we put three little dots. And this means continued, because, as we’ve said, there’ll be infinite number of different elements within this set. So we can say that if 𝑋 is a set of odd numbers, then 𝑋 can be written as nine, 11, 13, et cetera. And I’ve put that inside of our curly brackets, which are part of our set notation and tells us that it represents a set of values.