How do I even? (3 Viewers)

[Gods_Spear]

I was doing the 2020 Maths Extension HSC and the paper was relatively easy (other then 14 b iii, if you get that question right under exam pressure you are the god of math, like what is that question???? Like i got it once I checked the solutions but how do you spot that stuff??) but I had no idea how to do any of 14 a. I don't remember studying it, i think its the binomial expansion stuff but how should I study for it? What would it be under in atomi or the textbook?

This is definitely a big gap for me in ext 1. What are the chances they assign this many marks to it again this year?