# Matrix Issue

• Oct 6th 2010, 01:43 PM
Quacky
Matrix Issue
The matrices A, B and C represent 3 transformations. By combining the three transformations, in the order A, then B, then C, a simple, single transformation is obtained which is represented by the matrix R.

Find R.

$A = \begin{pmatrix} -2&1\\7&-3 \end{pmatrix}$
$B = \begin{pmatrix} 4&1\\-5&-1 \end{pmatrix}$
$C =\begin{pmatrix} 3&1\\2&1 \end{pmatrix}$

I have tried working out the matrix ABC but that gives an incorrect solution. I don't really know how to approach this. The answer is the identity matrix, it says in the textbook. Thanks in advance for any help.
• Oct 6th 2010, 01:56 PM
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Quote:

Originally Posted by Quacky
The matrices A, B and C represent 3 transformations. By combining the three transformations, in the order A, then B, then C, a simple, single transformation is obtained which is represented by the matrix R.

Find R.

$A = \begin{pmatrix} -2&1\\7&-3 \end{pmatrix}$
$B = \begin{pmatrix} 4&1\\-5&-1 \end{pmatrix}$
$C =\begin{pmatrix} 3&1\\2&1 \end{pmatrix}$

I have tried working out the matrix ABC but that gives an incorrect solution. I don't really know how to approach this. The answer is the identity matrix, it says in the textbook. Thanks in advance for any help.

"A, then B, then C" corresponds with CBA. I haven't done the calculation but I'm guessing that will work for you.
• Oct 6th 2010, 02:01 PM
Quacky
WOOPS! It's a good thing you didn't complete the question - your correct working lead to the correct answer, which I realised was NOT the identity matrix, although it is very similar. Thanks again.