i am a a2 student doing edexcel maths.
Last year i got 78 ums for c1 and 68 ums for c2, I'm retaking them both this year to get them my ums in 90's, any tip on topics that are not really looked at in C3 and C4, apart from of course the series and sequences
Majority of C1 is basic algebra that should be embedded into the back of your mind by now. I did MEI so I'm not sure on the different topics you might of done but C2 should especially mostly be piss easy considering the amount of intergration and differentiation you do in C3/C4.
Having studied C3 and C4 you can just flick through C1 and C2 and take a note of the topics and just skip to past papers.
The only thing I can really remember are sectors and stuff from C2.