Unit 2 Sequences, expressions and formulae
2.3
Using the nth term
The nth term formula is another way to write the position-to-term rule. You can work out a sequence using the nth term by drawing a table. When the nth term is 2n + 1, the first five terms are: Term number (n)
1st
2nd
3rd
4th
5th
2×n
2×1=2
2×2=4
2×3=6
2×4=8
2 × 5 = 10
2×n+1
2+1=3
4+1=5
6+1=7
8+1=9
10 + 1 = 11
So the first five terms of the sequence are 3, 5, 7, 9, 11.
1
Complete the tables to work out the first five terms of each sequence.
a nth term is n + 3. Term number (n) n+3
1st
2nd
3rd
4th
5th
1+3=4
2+3=5
3+3=6
4 + 3 = ......
5 + 3 = ......
So the first five terms of the sequence are 4, 5, 6, . . . . . . , . . . . . . b nth term is n + 9 Term number (n) n+9
1st
2nd
3rd
4th
5th
1 + 9 = 10
2 + 9 = ......
3 + 9 = ......
4 + 9 = ......
5 + 9 = ......
So the first five terms of the sequence are 10, . . . . . . , . . . . . . , . . . . . . , . . . . . .
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