It would be the vertical distance between that point and the line. Or you could think of it the y value of this point and the y value of the line. And you just keep going all the way to the end point between the y value of this point and the y value of the line. So this error right here, error 1, if you think about it, it is this value right here, this y value. It's equal to y1 minus this y value. Well, what's this y value going to be? Well, over here we have x is equal to x1.