Now instead, suppose that I graph volume over one over P. Well, how would that look? Well, if I grab the volume over one over P, whenever this guy increases, this guy increases by the same ratio amount. And that's because volume times pressure gives you a constant. If this increases by say, two times, then this must decrease by two times. That's why this guy is a straight line, the slope is constant, versus on this graph, the slope varies, it changes. And if you wanted to find the slope, you would have to use calculus and approximate it using lines tangent to any point on the line.