UPDATE: If you’re looking for the solutions to the 2021 exam, check here.
I didn’t end up having time to complete these before the officially published solutions came out. However, I still wanted to do the working out myself, and possibly provide a different approach to solving some of the questions on the exams.
Overall I feel like this test had a lot of relatively easy questions for most syllabus topics, but the harder questions were on the very difficult side. The binomial question was a bit tricky, I feel, because of the expansion within the expansion required, but if you can see how that unfolds you can easily equate the proper coefficients. I did appreciate using that result in an application to combinatorics, as well. The last question part (iii) was also pretty difficult, but if you can find that relationship between each next triangle, you should be able to finish it up. I also liked the tie in of a geometric series here.
If you have any questions about the working or solutions, please feel free to let me know!
I’m looking forward to going over the 2019 exam and seeing how they decide to conclude the old syllabus!
Download the PDF file here (file size is approximately 4.3 MB):
2018 HSC Mathematics Extension 1 Exam Solutions