The sum of the first n n\,n terms of a series is
12n(2a+(n−1)d). \frac{1}{2}n(2a + (n-1)d). 21n(2a+(n−1)d).Prove that the series is an arithmetic series with first term a a\,a and common difference ddd.
326 exam-style questions on Edexcel A Level Maths Sequences and Series, covering 3.1 Arithmetic Sequences, 3.2 Arithmetic Series, 3.3 Geometric Sequences, 3.4 Geometric Series, 3.5 Sum to Infinity, 3.6 Sigma Notation, 3.7 Recurrence Relations, and 3.8 Modelling with Series. Each one has a worked solution and a mark scheme showing where the marks go.