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Published byArline Hardy Modified over 9 years ago
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Journey to the n th level
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A few sequences… What comes next? 9, 13, 17, 21…. ….. 25, 29 term to term rule: add 4
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A few sequences…What comes next? 20, 15, 10, 5…. ….. 0, -5 term to term rule: subtract 5
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A few sequences…What comes next? 1, 10, 100, 1000…. ….. 10,000, 100,000 term to term rule: x 10
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10, 20, 30, 40, 50, 60, 70…… n = 1 st 2 nd 3 rd 4 th 5 th 6 th 7 th The position to term rule is: whichever term I’m interested in X 10 n nth term = n x 10 or 10n n th term expressions
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4, 8, 12, 16, 20, 24, 28…… The position to term rule is: whichever term I’m interested in X 4 n nth term = n x 4 4n n= 1 st 2 nd 3 rd 4 th 5 th 6 th 7 th n th term expressions
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What is the position to term rule: 2, 4, 6, 8, 10 …. nth term = 100, 200, 300, 400…. nth term = 100n What’s the 7 th term? What’s the 10 th term? What’s the 18 th term? n x 2 = 2n 700 1,000 1,800 for the last sequence (100n)
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Sequences the nth term D gradeC grade generate terms of a linear sequence using term-to- term and position-to-term rules generate terms of a sequence using term- to-term and position-to- term rules write an expression for the nth term of a simple arithmetic sequence, generate sequences from practical contexts and write and justify an expression to describe the nth term of an arithmetic sequence
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Questions to try Page 68 Exercise 7A Questions 1 a, c, e & g Question 2 a, c, e & g Question 3 Question 4 Question 6 Finished? CHECK your answers with a friend and on page 282 Additional challenges available! Need help? Just ask
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more complicated…. 5, 8, 11, 14, 17, 20 ….. +3 common difference is 3 1234567891011121314151617 nth term =3n+ 2 1234567891011121314151617 + 2 -3 n = 0 1 st 2 nd 3 rd 4 th 5 th 6 th 2,
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6, 11, 16, 21, 26… Step 1: Common difference? nth term = 5n Step 2: How has the table been shifted? + 1 To work out the rule for the nth term of a sequence 012345678910111213141516 012345678910111213141516 + 1 n= 0 1 st 2 nd 3 rd 4 th 5 th 1, Clip 112 Finding The Nth Term.avi
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Extension: h)1, 9, 17, 25, 33.. i)-2, 8, 18, 28, 38.. j)-2, -4, -6, -8, -10.. k)1, 4, 9, 16, 25.. l)3, 6, 11, 18, 27.. a)3, 5, 7, 9, 11, 13…. b)12, 20, 28, 36, 44…. c)19, 29, 39, 49, 59…. d)7, 10, 13, 16, 19…. e)14, 20, 26, 32, 38…. f)55, 60, 65, 70, 75… g)8, 17, 26, 35, 44…. 2n+1 8n+4 10n+9 3n+4 6n+8 5n+50 9n-1 8n-7 10n-12 -2n n2n2 n 2 +2
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Questions to try Page 71 Exercise 7B Questions 1 a, c, e & g Question 3 a, c & e Question 4 Question 5 Finished? CHECK your answers with a friend and on page 281 Additional challenges available! Need help? Just ask
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What sequence rule would the pattern of matchsticks follow: 2n + 1 +2 -2 1, 3, 5, 7…
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You own a taxi company that charges as follows: £3.50 for calling the cab 20p for every minute of journey time 1.Work out a formula for the cost of a journey that’s n minutes long 2.Use your formula to cost a journey of 2 hours 20n + 350or 0.20n + 3.50 20p x minutes + call charge= Total cost 0.20 x 120 + 3.50 = £27.50
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