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Mathematics 17 Online
OpenStudy (anonymous):

find non zero matrices A,B and C such that AC=BC find non zero matrices A,B and C such that AC=BC @Mathematics

OpenStudy (zarkon):

I'm betting there is more to this problem.... Let A=B

OpenStudy (zarkon):

for example let A=B=C=I

OpenStudy (anonymous):

yes u r right A is not equal to B

OpenStudy (zarkon):

\[A=\left[\begin{matrix}1 & 0 \\ 0 & 0\end{matrix}\right]\] \[B=\left[\begin{matrix}0 & 0 \\ 1 & 0\end{matrix}\right]\] \[C=\left[\begin{matrix}0 & 0 \\ 1 & 1\end{matrix}\right]\]

OpenStudy (anonymous):

are u take these matrices by applying any rule if so then plz tell me how such matrices are taken

OpenStudy (zarkon):

the only thing I really need to do was to make sure that C was not of full rank

OpenStudy (anonymous):

what is meant by 'C is not of full rank'?

OpenStudy (zarkon):

In the case of square matrices ...I needed to make sure C was not invertible. then it was easy to find and A and B that worked

OpenStudy (anonymous):

u mean A and B must be invertible but C is not invertible and we take any matrices by applying this rule

OpenStudy (zarkon):

no...since clearly the none of the matrices I gave are invertable

OpenStudy (anonymous):

ok we can take only singular matrices of any order and with different entries isn't it?

OpenStudy (zarkon):

\[A=\left[\begin{matrix}1 & 0 \\ 0 & 1\end{matrix}\right]\] \[B=\left[\begin{matrix}1 & 0 \\ 1 & 1\end{matrix}\right]\] \[C=\left[\begin{matrix}0 & 0 \\ 1 & 1\end{matrix}\right]\]

OpenStudy (zarkon):

the above works...and A,B are both invertable

OpenStudy (anonymous):

in this case C is singular which i have already told

OpenStudy (zarkon):

yes...C has to be singular otherwise it is impossible

OpenStudy (anonymous):

briefly A and B may or may not be singular but C must be singular am i right?

OpenStudy (zarkon):

no

OpenStudy (anonymous):

what do u want to say?

OpenStudy (zarkon):

sorry..yes...A,B could be singular or not, but C has to be singular

OpenStudy (zarkon):

but your choice of A and B is still limited...not all A,B work

OpenStudy (anonymous):

thanks a lot

OpenStudy (zarkon):

no problem

OpenStudy (anonymous):

how choice of A and B is limited

OpenStudy (zarkon):

it has to do with the null space of C

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