[AAHL][AASL] Revision Guide: Topic 1.1

Henlo kiddos!

Really hope everyone's doing great. Tis is the time of the year when N23s have barely started the course (and I see many of them are doing sequences and series) while M22s better start revising for the exams. Just a friendly reminder: unless you've been told explicitly by your school that exams won't go forward, please do yourself a favour and study NOW if you wanna do well.

Due to popular demand (~40 votes in the Mocks server, not a small proportion) one of my focuses for this year is writing end-of-topic revision guides. I probably won't write these for EVERY SINGLE TOPIC, as some topics never show up as a grade 7 question (I'm looking at you, correlation). For more info re: the structure and the purpose of this booklet, read the second page, but here's a tl;dr:

• Different target audience - this booklet is aimed at everyone, including those shooting for a 7. Some questions are deliberately set at that level. For more accessible questions, please check out the Survival Guide.
• Some examples are included, but either to demonstrate an important point or to showcase my reasoning when dealing with more complex questions.
• I assumed that y'all have seen the topic before and could still recall most basic things from the topic. Space is precious and I don't wanna waste your time with "boring" derivations that you should've done in class, for example, proofs for the finite sum of an arithmetic or a geometric series. You can easily look them up online.

Looking at the size of sequences and series (AA 1.1), it's gonna be a while until I finish writing everything alongside my courses. Instead of burning myself out I'll post these as I go along, probably once every 2 weeks. 

Disclaimer: if your teacher teaches at the same pace as this guide, it's a very good warning that you need to do more practice. If you find these questions too challenging, it's a good idea to check other resources. For more procedural exercises, I recommend Solomon Worksheets, available on PMT.

Last words: please spread the word if you find this helpful. DMs are open for suggestions, or you can send questions directly on the Mocks server. You may also fancy buying me a coffee, that'd be greatly appreciated! :D

Credits: AdventurousAndrew#7499