topic badge
AustraliaVIC
VCE 11 General 2023

6.06 Powers of matrices

Worksheet
Powers of matrices
1

State whether each of the following matrices could be raised to a power:

a

A=\begin{bmatrix} 5 & 0 \\ 3 & 4 \end{bmatrix}

b

A=\begin{bmatrix} 5 & 4 & 1 \\ 0 & -1 & -2 \end{bmatrix}

c

A=\begin{bmatrix} 0 & 4 \\ 3 & -2 \\ -5 & 5 \end{bmatrix}

d

A=\begin{bmatrix} -2 & -5 & -4 \\ 2 & -3 & 5 \\ 0 & -1 & 3 \end{bmatrix}

2

For each matrix, find A^2:

a

A=\begin{bmatrix} 0 & -1 \\ -2 & 1 \end{bmatrix}

b

A=\begin{bmatrix} 2 & 1 & 0 \\ -4 & 5 & -1 \\ 3 & -2 & -5 \end{bmatrix}

3

Consider A=\begin{bmatrix} -1 & 0 \\ 5 & -2 \end{bmatrix}.

a

Find A^{2}.

b

Use the fact that A^{3} = A \times A^{2} to find A^{3}.

4

Consider A=\begin{bmatrix} 3 & 1 \\ -1 & 2 \end{bmatrix}.

a

Find A^{2}.

b

Use the fact that A^{3} = A \times A^{2} to find A^{3}.

c

Find A^{2} \times A.

d

Does A^{3} equal A^{2} \times A?

5

For each of the following square matrices, use your CAS calculator to find the indicated power, rounding each element to three decimal places where necessary:

a

A=\begin{bmatrix} 6 & -9 \\ 4 & 8 \end{bmatrix},\, A^{2}

b

A=\begin{bmatrix} -5 & 3 \\ 2 & -1 \end{bmatrix},\, A^{7}

c

A=\begin{bmatrix} 0.85 & 0.46 \\ 0.15 & 0.54 \end{bmatrix},\, A^{27}

d

A=\begin{bmatrix} -2 & 3 & 0 \\ -2 & 1 & 6 \\ 0 & 4 & 0 \end{bmatrix},\, A^{6}

e

A=\begin{bmatrix} 0 & 1 & 0 \\ 0 & 1 & 1 \\ 1 & 0 & 1 \end{bmatrix},\, A^{16}

f

A=\begin{bmatrix} 0.1 & 0.3 & 0.6 \\ 0 & 0.5 & 0.4 \\ 0.9 & 0 & 0.2 \end{bmatrix},\, A^{28}

g

A=\begin{bmatrix} 1 & -2 & 3 & 4 \\ 2 & 1 & -7 & 8\\ 3 & 5 & 8 & -6 \\ -8 & -1 & 10 & 9 \end{bmatrix},\, A^3

h

A=\begin{bmatrix} 0 & 0.4 & 0.7 & -0.1 \\ 0.9 & 0.8 & -0.7 & 0.2\\ -0.1 & 0.5 & 0.5 & 0.1 \\ 0 & 0.2 & 0.2 & 0.6 \end{bmatrix},\, A^{15}

i

A=\begin{bmatrix} 7 & 1 & 0 & 1 & 2 \\ 2 & 3 & 0 & 4 & 2\\ 1 & 2 & 4 & 1 & 4 \\ 2 & 1 & 4 & 3 & 0 \\ 0 & 5 & 2 & 1 & 2 \end{bmatrix},\, A^5

j

A=\begin{bmatrix} 1 & 1 & 1 & 0 & 0 \\ 0 & 0 & 0 & 1 & 1\\ 0 & 0 & 1 & 1 & 0 \\ 0 & 1 & 0 & 0 & 1 \\ 1 & 0 & 1 & 0 & 0 \end{bmatrix},\, A^{12}

k

A=\begin{bmatrix} 0 & 0 & 0 & 0.1 & 0 \\ 0.4 & 0 & 0.2 & 0.8 & 0\\ 0 & 0.5 & 0 & 0 & 0.6 \\ 0.3 & 0.3 & 0.3 & 0 & 0 \\ 0.2 & 0 & 0.6 & 0 & 0.4 \end{bmatrix},\, A^{27}

6

For each of the matrices below:

i

Find A^{20}, giving each element correct to three decimal places.

ii

Find A^{21}, giving each element correct to three decimal places.

iii

Hence or otherwise, describe the behaviour of the elements of matrix A as it is raised to larger powers.

a

A=\begin{bmatrix} 0.4 & 0 & 0.2\\ 0.2 & 0.9 & 0.5 \\ 0.4 & 0.1 & 0.3 \end{bmatrix}

b

A=\begin{bmatrix} 0\enspace & 0.1\enspace & 0\enspace & 0.6\\ 0.5\enspace & 0\enspace & 0.8\enspace & 0 \\ 0\enspace & 0.9\enspace & 0\enspace & 0.4 \\ 0.5\enspace & 0\enspace & 0.2\enspace & 0 \end{bmatrix}

Applications
7

The map shows four towns and the paths connecting them:

Let matrix A below, represent all of the single-step paths between the towns:

\begin{matrix} & \text{To} \\ \text{From} & \begin{matrix} \\& \begin{matrix} \text{Kingston} & \text{Ashland} & \text{Greenville} & \text{Dunham} \end{matrix} \\ \begin{matrix} \text{Kingston} \\ \text{Ashland} \\ \text{Greenville} \\ \text{Dunham} \end{matrix} & \begin{bmatrix} 0 \qquad & \qquad 1 \qquad & \qquad 0 \qquad & \qquad 0 \\ 1 \qquad & \qquad 0 \qquad & \qquad 1 \qquad & \qquad 1 \\ 0 \qquad & \qquad 1 \qquad & \qquad 0 \qquad & \qquad 1 \\ 0 \qquad & \qquad 1 \qquad & \qquad 1 \qquad & \qquad 0 \end{bmatrix} \end{matrix} \end{matrix}
a

Find A^{4}, the matrix that represents all possible four-step paths between the towns.

b

How many four-step paths can be taken from Greenville to Dunham?

8

Five friends are participating in a puzzle event. As part of the rules of the event, each person can only send messages to two other people. Let matrix A represent the possible communication pathways:

\begin{matrix} & \text{Receiver} \\ \text{Sender} & \begin{matrix} \\& \begin{matrix} \text{Aaron} & \text{Bill} & \text{Clara} & \text{Darrel} & \text{Eve} \end{matrix} \\ \begin{matrix} \text{Aaron} \\ \text{Bill} \\ \text{Clara} \\ \text{Darrel} \\ \text{Eve} \end{matrix} & \begin{bmatrix} \quad 0 \qquad & 1 \qquad & 1 \qquad & 0 \qquad & 0 \quad \\ \quad 0 \qquad & 0 \qquad & 1 \qquad & 1 \qquad & 0 \quad \\ \quad 0 \qquad & 0 \qquad & 0 \qquad & 1 \qquad & 1 \quad \\ \quad 1 \qquad & 0 \qquad & 0 \qquad & 0 \qquad & 1 \quad \\ \quad 1 \qquad & 1 \qquad & 0 \qquad & 0 \qquad & 0 \quad \end{bmatrix} \end{matrix} \end{matrix}

a

Find A^{2}, the matrix that represents all messages that can be sent in two steps.

b

Can Bill send a message to Aaron in a maximum of two steps?

9

A particular website is to be designed so that all website content is available to a user within three clicks. The webpage adjacency matrix A, representing available links between different parts of the website is given.

A=\begin{bmatrix} 0 & 1 & 1 & 0 & 0\\ 1 & 0 & 0 & 0 & 1\\ 1 & 0 & 0 & 1 & 0\\ 0 & 1 & 1 & 0 & 0 \\ 0 & 1 & 0 & 1 & 0 \end{bmatrix}

If every webpage can be reached within three clicks, then the matrix B = A + A^{2} + A^{3} will have no zero entries.

a

Find A^{2}.

b

Find A^{3}.

c

Find the matrix B= A + A^{2} + A^{3}.

d

Is every webpage able to be reached within three clicks?

10

The following map network shows the roads that connect three towns:

a

Create a 3 \times 3 matrix A, to represent the direct one-step paths between the three locations. For the rows and columns, use the order of Millen, Nowin then Oneslay.

b

Find A^{2}, which represents the two-step paths between the three locations.

c

How many two-step paths can be taken from Norwin to Millen?

11

The following map network shows connections between Joondalup, Perth, and Fremantle:

a

Create a 3 \times 3 matrix M, to represent the direct one-step paths between the three locations. For the rows and columns, use the order of Joondalup, Perth then Fremantle.

b

Find the matrix M^{2}, which represents the two-step paths between the three locations.

c

How many two-step paths can be taken from Freemantle to Jundalup?

Sign up to access Worksheet
Get full access to our content with a Mathspace account

Outcomes

U1.AoS3.3

matrix arithmetic: the definition of addition, subtraction, multiplication by a scalar, multiplication, the power of a square matrix, and the conditions for their use

U1.AoS3.9

add and subtract matrices, multiply a matrix by a scalar or another matrix, and raise a matrix to a power

What is Mathspace

About Mathspace