i barely passed the first adv task, went to getting 99% on prelims, here's a summary of my approach:
1. get baseline knowledge of everything
don't do textbook questions if you don't yet understand the content. for example, make sure you know how the derivative is derived from a limit, what it physically and geometrically represents, potential applications etc, so when you do questions you aren't questioning if you've done the question correctly and also garner a bit more intuition on why the processes that you are doing are significant. you will feel confused if you don't know why anything that is happening makes sense, getting some clarity into the processes definetly helps. you might want to prove the power rule for example, it isn't a difficult proof but it helps you understand why it works instead of doing things "because it works". again basic proofs and derivations when it is possible help a lot with this, it also means that when you get stuck on a question, you can bring it back to those basic proofs and definitions and recognise what went wrong / derive formulas based on a question, even if you haven't seen a particular technique that a question wants before.
you may also want to write notes, this can be helpful to an extent when there's a lot of content (personally i never wrote notes in math until uni, just due to there being more content and also to act as a summary since we don't have a clear cut textbook). however questions should by far supersede the amount of time you spend on notes, don't spend too much time on them.
2. basic operations
u can't do exam level papers if u can't apply basic operations. for example make sure that if you need to take a derivative, you don't need to consult the formula sheet every time, you should know power rule, chain rule, etc like the back of your hand. best way to do this is to just do a bunch of repetitive questions usually in a textbook, until it's like clockwork to do basic stuff. honestly there's no way around this, its just practice and is pretty much the bare minimum for success, half of the paper in math advanced is just doing these basic questions and operations. so make sure you've completed almost every single question in the textbook bar the enrichment questions for each topic before proceeding into harder questions.
3. past papers
after you've completed textbook work, literally all of your time should be spent on past papers. by the end of my hsc i did pretty much every new syllabus past paper i could find for math, thsc houses the majority of them. past papers allow you to apply the basics you learnt from the textbook in a variety of contexts, and realistically this is the best way to prepare for assessments by far. exposing yourself to as many exam questions as possible means that for 85% of scenarios, you've seen it before and can do the questions in far shorter time than would be required if you haven't seen a particular question type before. then you can allocate nearly all the exam time to the harder 2-3 questions on the paper that you might struggle with or haven't seen before. this means less time crunch, and more time that can be spent thinking of ways to approach the harder questions and checking your answers. you will definetly feel prepared having done 5-15 past papers in the few weeks prior to your assessment, provided that you adequately address the stumbleblocks you encountered in the papers and correct any mistakes in your exam technique (try to slow down if you can).
there pretty much comes a point where if you've done a certain amount of past papers, you can effectively feel like you've mastered a topic as you walk in the exam and have already seen 90% of the questions lmao (especially in math adv). by the time my math adv prelim rolled around i could finish the paper in an hour and a half since the questions types were super familiar to me and i swear half of the time internal papers all reuse questions over and over. so definetly try to saturate the majority of your study time with past papers.
4. stay ahead
always try to be one textbook chapter ahead of the class in work done. i did this and it made things so much easier, no or much less homework deadlines to worry about, and any time the teacher was explaining things it was just doubling down on the knowledge i gained from reading the textbook and doing questions ahead of time. you don't have to finish the whole syllabus in a month or anything, but putting in an additional few hours before the term starts means that the consistent work you would have put into the subject normally accelerates you one topic ahead of the classwork, which is super helpful.
im probably forgetting half of what else i did to improve lmao but yea just put in as much time as feasibly possible into the subject doing past papers, and provided that you do well on those there's really not mcuh else you can do to improve, just make sure you take a step back, slow down and really question every line of working out you do to reduce the number of mistakes you make. there was plenty of people at my school who didn't necessarily do well in the first couple of assessments in math adv yet ended up with a band 5-6, it's definetly not too late provided you double down and improve on your current weaknesses and put in the necessary time to get better.
