Term-to-term rule with a starting value (3 marks)

GCSE · Mathematics · WJEC · A23 — Generate sequences from term-to-term and position-to-term rules

Question

Question. A sequence is generated by the rule “multiply the previous term by 2 and subtract 1”. The first term is 3. Find the fourth term of the sequence.

Mark scheme.

M1: $u_2 = 2 \times 3 - 1 = 5$ .
M1: $u_3 = 2 \times 5 - 1 = 9$ .
A1: $u_4 = 2 \times 9 - 1 = 17$ .

Common error: applying the rule only twice and answering 9; or computing $2 \times 3 - 1 \times 2 - 1 = …$ (operator precedence error).

3 marks · take your time before peeking.

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Generated by TopMyGrade AI · cross-check official sources before relying on the mark-scheme phrasing.