What I mean by that is if you move your pen and it hits only once then yes it's a function, if it hits more than once, no it's not a function. If a graph passes the vertical line test then it is a function. If you don't remember anything else from this video what I hope you remember is the vertical line test. Very similar here when I use my pen and move it vertically across the graph there is nowhere where I'm hitting the shape twice, I'm only hitting it once therefore d, yes, is also a function. So this case yes it's a function because that x value only has one y value. Check it out everywhere I move my pen it only crosses the graph once right, I'm never hitting this graph line more than once. Here is a couple that are a little bit different when you use your vertical line test down here. Definition of a function: Every x value has a unique y.
#Vertical line test how to#
It explains how to tell if a graph represents a function. If you think about it, the vertical line test is simply a restatement of the definition of a function. That again means that x has two y values, not a function. Vertical Line Test 240,240 views This precalculus video tutorial provides a basic introduction into the vertical line test. Vertical oh-oh! You can see your pencil hits places where your vertical line crosses the graph in more than one place.
Let's try this next graph use your pencil and make sure it's vertical and not horizontal. Watch popular content from the following creators: kat(talkcleantome), Math Videos with Sir. This x value right here whatever it is has tons the y values there is a y value, there is another one, there is no one it's not a function. Discover short videos related to vertical line test on TikTok. I just hit my graph like one two three four like 10 times whatever it doesn't matter, I hit it more than once so this is not a function. And you'll see in this graph there's like tons of places, check it out. What you would do with the graph on your paper is take your pencil lay it down there and then move it across the graph, see if you hit any places on this graph where your pencil crosses the squiggly in more than one place. Think of this like your pencil this is a big pencil. So what I'm going to do is go through these graphs and draw vertical lines and if it hits, if my vertical line hits the graph more than once in each line then it's not a function, because that represents a place where an x value has two y values. It's using what's called the vertical line test. So what I want to talk about here is how you can tell that something is a function just based on the graph and you'll see it's actually pretty easy. One of the neat things about functions is that we know something is a function if each x has exactly one y but sometimes you are not given the points, you are not given numbers, all you are given is a funny graph.
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