Find A-2B

**kwtolley** · July 19th 2006, 08:21 PM

A= 5 1 B= -1 3
3 2 4 1 Find A-2B
My answer is -1 3
4 1 I don't think this is right after using excel, thanks for checking.

**CaptainBlack** · July 19th 2006, 08:48 PM

Originally Posted by kwtolley

A= 5 1 B= -1 3
3 2 4 1 Find A-2B
My answer is -1 3
4 1 I don't think this is right after using excel, thanks for checking.

$ A= \left[ \begin{array}{cc} {5}& {1}\\ {3}& {2} \end{array} \right],\ B= \left[ \begin{array}{cc} {-1}& {3}\\ {4}& {1} \end{array} \right]. $

so:

$ A-2B= \left[ \begin{array}{cc} {5}& {1}\\ {3}& {2} \end{array} \right]- 2 \times \left[ \begin{array}{cc} {-1}& {3}\\ {4}& {1} \end{array} \right] $

$ = \left[ \begin{array}{cc} {5}& {1}\\ {3}& {2} \end{array} \right]- \left[ \begin{array}{cc} {-2}& {6}\\ {8}& {2} \end{array} \right]= \left[ \begin{array}{cc} {7}& {-5}\\ {-5}& {0} \end{array} \right] $

**kwtolley** · July 20th 2006, 12:35 AM

I thought mt answer was wrong. thanks again

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Find A-2B

thanks

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