An arithmetic progression has first term a a\,a and common difference bbb.
Prove that the sum of the first N N\,N terms of the progression is
SN=12N{2a+(N−1)b} S_N = \frac{1}{2}N\{2a + (N-1)b\} SN=21N{2a+(N−1)b}Practise Edexcel A Level Maths 3.2 Arithmetic Series with exam-style questions for A Level Maths. 38 questions, matched to the Edexcel A Level Maths (9MA0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.