The bridging courses are usually set up for those who have done 2u. You could still do it with general although you will find it much harder. I would suggest as others have that you do some preparation and do the course. If you don't go very well then (if you go to UNSW) you can always do the general mathematics course first.
From UNSW Website:
http://www.unsw.edu.au/futureStudents/undergrad/sad/bridgeprog.html
Mathematics Bridging Course
Some university programs assume an existing knowledge equivalent to HSC Mathematics Extension 1 (or "3 unit"). The aim of the Mathematics Bridging Course is to bridge the gap between the HSC Mathematics course (not the General Mathematics course) and what is required for these university programs by teaching relevant topics of the HSC Mathematics Extension 1 course. Your performance in the Maths Bridging Course examination may mean you are properly prepared for entry directly into MATH1131 which is a compulsory course in all engineering programs, mathematics programs and many science-based programs at UNSW. To enter MATH1131 it is assumed that you have the knowledge and understanding equivalent to:
* a result of about 90 in HSC Mathematics ("2 unit"). (This course is not the pre-2001 HSC course Mathematics in Society or the post-2001 HSC General Mathematics), or
* a combined mark of over 100* in HSC Mathematics ("2 unit")/HSC Mathematics Extension 1 ("3 unit"), or
* a satisfactory grade in the UNSW Mathematics Bridging Course.
*a combined mark of over 115 is more realistic
If you do not have the above assumed knowledge for entry to MATH1131 you are advised to first complete the one session course, General Mathematics 1B, MATH1011.