I am grading differential equations finals. In this subject almost every single answer can be checked by plugging it back into the equation to see if it works. I even instruced students to "check your worK" on the final. So far out of 112 problems graded, only one answer has been checked, and accuracy is running only about 40%. Don't be that person who gets a 60 instead of a 90 because they refused to check an answer, to learn that it needed correcting. i.e. don't be so foolish as to claim that y = x^2 is a solution of y''-2y'+y = x^2, just because thats what you got when you went through the procedure. try it and see. then do it again. not checking your answer means you think you are perfect. Is that likely?