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Standard Level

6.01 Introduction to sequences

Worksheet
Explicit sequences
1

Identify the following sequences as finite or infinite:

a
1, 2, 3, 4, 5, 6
b
-1, -2, -3, -4, -5, -6, \ldots
2

What is the third term in the sequence 4, - 5, 6, - 7, 8?

3

Find the next number in the sequence 16, 36, 64, 100, 144, \ldots

4

Find the first five terms of the following sequences. Round the terms to four decimal places where necessary.

a
u_n = \dfrac{n + 4}{n + 3}
b
u_n = \dfrac{5 n - 1}{n^{2} + 5}
c
u_n = \left(\dfrac{1}{2}\right)^{n} \left(n - 3\right)
d
u_n = 3 n - 3
e
u_n = - 2^{n}
f
u_n = \left( - 2 \right)^{n} \left( 3 n\right)
g
u_n = \dfrac{1}{\sqrt{n}}
h
u_n = \left(1 + \dfrac{1}{n}\right)^{n}
5

For the sequence 3, 0.3, 0.03, 0.003, \ldots , write a formula for the nth term of the sequence, u_n, in terms of n.

Applications
6

Christa deposits \$1 into a new bank account while Jenny deposits \$38 into a new bank account. The next day, Christa adds \$2 to the account, and doubles how much she adds each day thereafter. Jenny adds \$5 each day.

a

Fill in the amount Christa had in the account each day for the first four days.

b

Fill in the amount Jenny had in the account each day for the first four days.

c

On which day will they have the same amount of money?

7

For a photo, the staff at a company have been arranged such that there are 9 people in the front row and each row has 2 more people than in the row in front of it.

a

Write a formula for u_n in terms of n.

b

How many people are in the 10th row?

8

A basketball is dropped onto the ground from a height of 15 metres. On each bounce, the ball reaches a maximum height of 55\% of its previous maximum height.

a

Write a formula for u_n, for the height reached on the nth bounce in terms of n.

b

How high does the basketball reach after the 5th bounce? Round your answer to two decimal places.

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