Brackets and interval notation
Brackets around arguments, numerators, coordinates, intervals. Round vs square has to be unambiguous.
What cost marks Exam 1
Missing brackets around $\cos(3x)$ and around a quadratic numerator made the answer ambiguous (Q1). A "rounded square" bracket on an interval couldn't be marked (Q5c).
What cost marks Exam 2
Flagged everywhere. An interval written $[1,-1]$ without proper brackets reads as two separate terms. Coordinates always need brackets.