This is the graph of y is equal to f of x. This is the graph of y is equal to g of x. And we already know something, or we know ways to represent the area under the curve y equals f of x between these two points, x is equal to a and x equal to b. So this area right over here, this area right over here, between the curve and the x axis, between x equals a and x equals b, we know we can write that as the definite integral from a to b of f of x dx. And we can do the same thing over here. We could call this area, let me pick a color that I have not used. Well, this is a slightly different green.