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. I could call this area right over here, the area under the curve y is equal to g of x, and above the positive x axis between x equals a and x equals b, we could call that the definite integral from a to b of g of x dx. Now, given these two things, let's actually think about the area under the curve of the function created by the sum of these two functions. So what do I mean by that?