Measuring segments

What is BD? So, when they're just saying BD, they're saying literally the length of segment BD.

So they're saying the length from point B to point D. B is sitting here at negative two, D here is at five. So, you're looking at really the distance between negative 2 and 5. You literally could just say, well, that's going to be 5, that's kind of our endpoint, minus negative 2.

So, 5 minus negative 2 is the same thing as 5 plus 2, or 7. Another way you could literally just count it out. Count out the distance; you go one, two to get to zero, three, four, five, six, seven to get all the way to five.

Or you could say, look, I gotta go two to the right just to get to 0, and I gotta go 5 more to the right to get to D. So that's going to be 7.

Let's do a couple more. What is BD again? Well, here we're going from 1 to 4. The distance between 1 and 4 is three.

And then let's do one more. What is AD? So A is at negative five, D is all the way at four. So we're going from negative five to zero, which is five, and then we're going to go four more; five plus four is nine.

Or you could say, hey look, we start at negative five, we end up at four. Four minus negative five is the same thing as four plus five, which is 9.