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iGCSE (2021 Edition)

17.08 Sequences

Worksheet
Sequences
1

For each of the following sequences, find the indicated term:

a

Third term in the sequence: 2, - 4 , 6, - 8 , 16, \ldots

b

Fourth term in the sequence: 3, 3.5, 4, 4.5, 5, 5.5, \ldots

c

Fifth term in the sequence: 5, 4, 3, 2, 1, 0, - 1 , \ldots

2

If T_n describes the nth term of the following sequences , find the indicated term:

a

T_3 in the sequence: 4, - 5 , 6, - 7 , 8, \ldots

b

T_4 in the sequence: 200, 20, 2, 0.2, 0.02, \ldots

c

T_5 in the sequence: 1, 2.5, 4, 5.5, 7, 8.5, \ldots

d

T_3 + T_5 in the sequence: 6, - 8 , 9, - 10 , 11, \ldots

e

2 T_2 - T_4 in the sequence: 9, 12, 15, 18, 21, \ldots

f

- 4 \left(T_3 + T_4\right) in the sequence: 1, 4, 5, 9, 14, 23, \ldots

3

In the sequence 5, - 5 , 7, - 7 , 9, - 9 , \ldots , find n if T_n = 7.

4

For each of the following sequences:

i

Describe the pattern in words.

ii

Find the next number in the sequence.

a

- 1 , 1, 3, 5, 7, \ldots

b

64, 32, 16, 8, 4, 2, \ldots

c

2, - 4 , 6, - 8 , 10, - 12 , \ldots

Explicit rules
5

Determine whether the following are explicit relations:

a

b_n = b_{n - 1} b_{n - 2}

b

d_n = n^{2} + 3 n + 8

c

a_n = 8 a_{n - 1} + a_1

d

c_n = 3 n^{2}

6

For each of the following explicit rules, state the first 5 terms of the sequences in order starting with n=1:

a

b_n = 5 n - 2

b

s_n = n^{2} + 6

c

t_n = 2 n^{2} + n - 3

7

For the following sequencesn state the explicit rule that describes T_n in terms of n.

a

A sequence starts with a first term of 1300 and each subsequent term increases by 2.5\% of the previous term.

b

A sequence starts with a first term of 44 and each term is 77 more than the previous term.

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Outcomes

0580C2.7

Continue a given number sequence. Recognise patterns in sequences including the term to term rule and relationships between different sequences. Find and use the nth term of sequences.

0580E2.7

Continue a given number sequence. Recognise patterns in sequences including the term to term rule and relationships between different sequences. Find and use the nth term of sequences.

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