For those that have missed or need help with arithmetic and geometric series, watch these. They are a collection of tutorials covering this entire topic
https://www.mathsgenie.co.uk/a-level-pure-sequences-and-series.html
Arithmetic sequences -
Introduction. This video introduces the idea and helps you understand where the formula come from
More likely exam question - This video covers the more likely situation of problem solving in arithmetic sequences, using simultaneous equations
Geometric series
Proof of formula - for those interested
Common exam question - This video covers the more likely situation of problem solving in arithmetic sequences, using simultaneous equations
Binomial expansion
Binomial expansion - This is a very long video but covers absolutely everything. Watch with breaks.
Exam Questions - Binomial expansion for positive integer powers