# Matrix help

• January 30th 2007, 11:45 PM
kwtolley
Matrix help
Find 3A-B when
A= 2 -1
3 0

B= 4 -2
5 1 my answer is 2 -1
4 1 is this right, thanks for checking and helping me also.
• January 31st 2007, 02:15 AM
CaptainBlack
Quote:

Originally Posted by kwtolley
Find 3A-B when
A= 2 -1
3 0

B= 4 -2
5 1 my answer is 2 -1
4 1 is this right, thanks for checking and helping me also.

$A=\left( \begin{array}{cc} 2&-1 \\ 3&0 \end{array}\right)$

$B=\left( \begin{array}{cc} 4&-2 \\ 5&1 \end{array}\right)$

Then:

$
3A-B= 3 \left( \begin{array}{cc} 2&-1 \\ 3&0 \end{array}\right)-\left( \begin{array}{cc} 4&-2 \\ 5&1 \end{array}\right)
$
$
=\left( \begin{array}{cc} 3\times 2-4&3\times(-1)+2 \\ 3 \times 3-5&3 \times 0-1 \end{array}\right)
$
$
=$
$
\left( \begin{array}{cc} 2&-1 \\ 4&-1 \end{array}\right)
$

RonL
• January 31st 2007, 07:56 AM
kwtolley
thanks again
Thats what I had, but I liked the way you broke it down. thanks so much.