I watched Iron Man 3 today, and wonder what this formula is about. Is it an important topic of physics? You know, like Transformers: Dark of the Moon, as I can recall, when an answer of some formula (problem) is got, an amazing weapon is invented. But I don't see any relationship in this movie. The picture is below:
This formula was the problem that Dr. Hansen needed to solve to fix the flaws with the Extremis virus. As you saw in the movie, many people who are subjected to the virus reject it and die violently. Dr. Hansen's attempts to solve it always failed, but she knew Tony Stark was smart enough to do it. So the whole plot of the movie was her and Killian attempting to force Tony to solve it, and thus fix the flaws of the Extremis virus.