So we are taking, I'll just rewrite this statement, instead of writing f of x I'll write x squared, so the definite integral from 1 to 4 of x squared dx, well, we're just going to have to figure out what the antiderivative is. So if f of x is equal to x squared, what is capital F of x equal to? What is the antiderivative? Well, you might remember from your power rules that if you take the derivative with respect to x of x to the third, you are going to get 3x squared, which is pretty darn close to x squared except for this factor of 3, so let's divide both sides by 3. And you get the derivative of x to the third divided by 3 is indeed x squared, or you could say that this is the same thing as the derivative with respect to x of x to the third over 3. So what is the derivative of this? It will be 3 times 1 third, and then you'll decrement the power, it will just be x squared.