This is in essence exactly the same procedure that the others have used, but with slightly different symbols (my old calc teacher used to call it "tricky" substitution)...
choose u=x-4. This means that du=dx, but it also means that u+4=x. As a result we have the following integral:
your right, it should be x-4. sorry about the typo. The 8 got dumped into the arbitrary constant that is added to the end. Any time you have an antiderivative with spare constants lying around you can do that. For example if your antiderivative was , then the indefinite integral could be written as . You'll notice that I switched from c to C to show this "dumping".