Hi!
For me personally, I used to be quite average at mathematics in prelim and got around a rank of 30 by my HY, so pretty much in the middle of my cohort. But by trials I managed to get into the top 10 by doing some things that I hope may help you personally:
1. The most important thing I did for me was to sort of seek to understand the content deeply rather than trying to memorise formulae. I did this a lot by watching videos by Eddie Woo (<3) who goes into more detail than what is really needed like this:
https://www.youtube.com/watch?v=tt2DGYOi3hcI found that this video really changed my outlook on mathematics as well. Here, he says that calculus shouldn't be the memorisation of rules and he implies that it should actually be understood, and that sort of mindset is something I tried to carry with all other topics I tackled.
I pretty much watched more of his videos on the commute to and from school and sometimes in my spare time. I found doing the questions and learning about other topics became easier overtime.
I guess since you might want to revise on prelim stuff you might be able to find some of his videos online? :O
But doing something like this would mean you would have to sacrifice your commute or other spare time so I didn't do this for all topics but it helped a lot in my of understanding 2U maths and remembering it
EDIT: Watching it on 1.25x, 1.5x or 2.0x speed + captions helped with the time-management for me
EDIT2: omg i found the first video I watched for this purpose and I think it was this guy's series on calculus:
https://www.youtube.com/watch?v=3BuIVJ558RY and first principle:
https://www.youtube.com/watch?v=KsqmAJ7Qyf8 he blew my mind
EDIT3: OMG AGAIN sorry for absolutely inundating you with videos but this one really encapsulates the mindset that Eddie Woo talks about:
https://www.youtube.com/watch?v=-YJSDJGyIaU2. I asked tons of questions. Like. The sort of kid that stays behind at recess and lunch for a bit every single time to ask the teacher questions about stuff that I didn't understand, and that also helped me with understanding some questions I had absolutely no idea.
3. Past-exam questions by topic are really good! One resource I find amazing for this is the Success One HSC Mathematics Past Paper + Solutions book. It's suuuper helpful by the fact that in the front and back pages it has a list of all topics, all the questions asked from 1992 onwards in the HSC exam on that topic, and the page number to do it (
highly recommended ). I just find that doing some exam type questions after/during learning a topic on that topic in the HSC is really sweet in getting more confident at it.