Mark576 said:
what sort of marks in extension 1 maths should you be getting if you want to do well in extension 2?
Marks I'd say 70-100? Depends on the difficulty of the exams your school sets. But being ranked high is a good indication if you should do 4u maths.
Regarding the workload, not that much if you manage your time well. It's not as much as everyone says/thinks and also it's not as hard as everyone exaggerates it to be. It's really rewarding if you do well, or even just average and is a major contributor to your UAI in the long run.
But if you do 4u maths, it will be good if you are "creative", as in you can think outside the box and try to do as much as you can of a question before giving up. You have to be able to visualise information questions give you (esp. in Mechanics and/or Conics)
But pretty much every other topic is just an extension from 3u maths (integration, harder 3u [as the name suggests it's hard], polynomials). Complex numbers is quite is easy as well it involves using vectors, imaginary numbers etc.
My advice is try the course, if you don't like you can drop it, if you do like then you are in for a treat, as you can only drop subjects/units not pick them up