Video6:Graph Lines x= -1
Math
Learning Graph Lines
Now we have X equals negative one. So that means that when we have our X and Y axis, we're going to put a dot on the negative one that is on the X axis. So I'm going to draw some lines here. That's one, two, three, four, on the other side, are my negative numbers. Negative one, negative two, negative three. Negative four. I'm going to put a dot on the X axis at negative one. Because I don't have any wise that means that this line is not going to touch the Y axis at all. So my X equals negative one will look like this. This is called a vertical line. Vertical lines go up and down. And you know that it's vertical because if I put another upside down V here, it forms an X so a vertical line is going to be an X equals line.
The slope for a vertical line, this is like if someone wanted to take your height, right? Just by looking at this line, I don't know what the height of it is. So the slope. Of X equals negative one or the slope of a vertical line. Is undefined. That is not the same thing as zero. The slope of a vertical line is undefined. Remember when we had Y equals negative one, that meant that our line touched the Y axis at negative one. So here are my positive numbers. Here are my negative numbers. So that means that I put a dot at negative one on the Y axis. That means that it's not going to touch the X axis at all. The slope of this line, as we discussed before, is equal to zero. Zero and undefined are two different things.