Consider the arithmetic sequence 8, 26, 44, $\ldots$ .

(a)     Find an expression for the ${n^{{\text{th}}}}$ term.

(b)     Write down the sum of the first n terms using sigma notation.

(c)     Calculate the sum of the first 15 terms.

(a)     $18n - 10\,\,\,\,\,$(or equivalent)     A1

(b)     $\sum\limits_1^n {(18r - 10)\,\,\,\,\,}$(or equivalent)     A1

(c)     by use of GDC or algebraic summation or sum of an AP     (M1)

$\sum\limits_1^{15} {(18r - 10) = 2010}$     A1

[4 marks]

An easy starter question, but few candidates seem to be familiar with the conventions of sigma notation.