C2: Geometric Series Dr J Frost Last modified: 24 th September 2013
Types of series 2, 5, 8, 11, 14, … +3 This is a: Arithmetic Series ? Geometric Series ? 3, 6, 12, 24, 48, … ? ?
Common Ratio ? ? ? ? ? ? ?
Common Ratio Exam Question May 2013 (Retracted) Hint for (a): the common ratio between the first and second terms, and the second and third terms, is the same. a b ? ?
Arithmetic SeriesGeometric Series Determine the following: 3, 6, 12, 24, … 40, -20, 10, -5, … ? ? ? ??
Another Common Ratio Example ?
Missing information The second term of a geometric sequence is 4 and the 4 th term is 8. The common ratio is positive. Find the exact values of: a)The common ratio. b)The first term. c)The 10 th term. The second term of a geometric sequence is 4 and the 4 th term is 8. The common ratio is positive. Find the exact values of: a)The common ratio. b)The first term. c)The 10 th term. ?
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Exam Question Edexcel June 2010 ? ? ? ? ?
Arithmetic SeriesGeometric Series ? ? Technically you could be asked in an exam the proof of the sum of a geometric series (it once came up!) So let’s prove it…
Geometric Series Find the sum of the first 10 terms. ? ? ? ? ? ? ? ?
Summation Notation ? ? ? ?
Harder Questions: Type 1 ? ?
Exercise 7D ? ? ? ? ? ? ? ? ? ?
Different types of series What can you say about the sum of each series up to infinity? This is divergent – the sum of the values tends towards infinity. This is convergent – the sum of the values tends towards a fixed value, in this case 2. This is divergent. This is known as the Harmonic Series Just for fun... ? ? ? ? ?
Sum to Infinity ? ?
Examples ? ? ?? ? ? ? ? ? ? ? ?
A somewhat esoteric Futurama joke explained
Another Example ? ?
Edexcel May 2011 ? ? ? ?
Exercises Exercise 7D Q6, 7 Exercise 7E Q8 Exercise 7F Q10