1.6.13 Standard formulae for arithmetic series (A-level only)

In an arithmetic sequence, the $r$ -th term is given by $u_r = u_1 + (r-1)d$ , where $u_1\,$ is the first term and $d\,$ is the common difference.

Show that the sum of the first $n\,$ terms of the corresponding arithmetic series is

S_n = \frac{n}{2}(2u_1 + (n-1)d)

[4]

In an arithmetic sequence, the $r$ -th term is given by $u_r = u_1 + (r-1)d$ , where $u_1\,$ is the first term and $d\,$ is the common difference.

Show that the sum of the first $n\,$ terms of the corresponding arithmetic series is

S_n = \frac{n}{2}(2u_1 + (n-1)d)

[4]

1.6.13 Standard formulae for arithmetic series (A-level only) Questions