Find the first term of the sequence.

Find the 21^st term of the sequence.

Find the sum of the first 30 terms of the sequence.

32 = u₁ + (10 − 1) × (−6)     (M1)

Notes: Award (M1) for correct substitution in correct formula. Accept correct alternative methods.

u₁ = 86     (A1)     (C2)

[2 marks]

u₂₁ = 86 + (21 − 1) × (−6)     (M1)

u₂₁ = −34     (A1)(ft)

Notes: Award (M1) for correct substitution in correct formula. Accept correct alternative methods. Award (M1) for a list of at least 5 correct terms seen. Follow through from their answer to part (a).

OR

u₂₁ = 32 + 11 × (−6)     (M1)

u₂₁ = −34     (A1)     (C2)

[2 marks]

\({S_{30}} = \frac{{30}}{2}(2 \times 86 + (30 - 1) \times ( - 6))\)     (M1)

Notes: Award (M1) for their correct substitution in correct formula. Accept correct alternative methods. For a list award (M1) for the correct addition of at least 10 terms.

\({S_{30}} = -30\)     (A1)(ft)     (C2)

Notes: Follow through from their answer to part (a).

[2 marks]

This question was very well answered by most candidates. Correct working was clearly shown. Many candidates used 32 as their first term and many others subtracted 6 rather than multiplied by -6, indicating a lack of attention in their algebraic notation and manipulation.

This question was very well answered by most candidates. Correct working was clearly shown. Many candidates used 32 as their first term and many others subtracted 6 rather than multiplied by -6, indicating a lack of attention in their algebraic notation and manipulation.

This question was very well answered by most candidates. Correct working was clearly shown. Many candidates used 32 as their first term and many others subtracted 6 rather than multiplied by -6, indicating a lack of attention in their algebraic notation and manipulation.