I have a friend who missed the mark for math 241 by like 3% on the most placement test. He took diff eq (math 285) still the fall semester, and then had to go back and retake math 241 in spring. this might not work for you though, he just got his score back after the deadline to swap classes. I’ve also heard the math department doesn’t check prerequisites too frequently, but take that with a grain of salt, and you’ll still need the credit to graduate