The intent of 4Unit maths is not like the other units of mathematics. They don't really want to see that you can just do the mechanics of mathematics (although they do teach you new and interesting stuff - like complex numbers) but to see that you can think like a mathematician and appreciate the beauty of numbers and work a complex problem that seems to have no relation to anything you have ever seen before.
It is the major work of mathematics.
In 4Unit English, the students have to move away from the set essay on "Journeys" and think outside the texts and write their own, showing the process whereby they came to their final product. 4U maths is like that. You are now thinking mathematically, analysing and showing how you got there utilising the skills anbd tools you have learnt to get you there. Some great mathematicians can see the answers before they get there, olthers can see the path, others just have to work the options before they reach the end point.
If you think you can do well in 4U maths by just doing questions and the mechanics of maths or reverse engineering the answers to previous questions, think again.
Certainly, understand the new stuff by doing questions but you need to aim for the creative thinking form of doing mathematics that is more creative than the set essay.
Good luck with it.