When we see a quadratic formula like f2 – g2, we almost always want to simplify it to see its parts better. This formula simplifies into (f + g)(f – g), so if we can get values for each of those
parenthetical statements, we can calculate the value of the whole. Statement (1) gives the value
of f + g when it is rearranged, but doesn’t give the value of f – g. We can cross off A and D.
Statement (2) gives the opposite: the value of f – g only. So it is not sufficient on its own - we can
cross off B - but the two statements are sufficient together, so C is the correct answer.