IGCSE Maths / Sequences and series

Finding a and d from two terms revision notes

Edexcel International GCSE Maths (4MA1), chapter 9: Sequences and series, specification point 3.1a. Part of the full course.

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An arithmetic sequence can be rebuilt from two known terms by finding the common difference, d, and the first term, a. The key is that the nth term is a + (n − 1)d, because reaching term n takes n − 1 jumps.

More lessons in Sequences and series

• Number sequences and term-to-term rules
• Finding a rule for a sequence
• Arithmetic sequences, a and d
• The nth term of an arithmetic sequence
• Using the nth term formula in reverse
• The sum of an arithmetic series
• Arithmetic series problem solving