Which Matrices Satisfy AB=BA for A=[1 0; 1 1]?

[gunnar]

I would appreciate if someone could help me with this one.

Matrix A=[1 0 ; 1 1]
I need to find all matrices that satisfy: AB=BA
How can I find them?
PLease help

 

[Galileo]

Try writing
B=\left(\begin{array}{cc}a & b \\ c&d \end{array}\right)

and check what the constraints on a,b,c and d are.

 

[gunnar]

did that. And put A(inverse)* [a b;c d] = C*A(inverse)

 

[dextercioby]

What does the inverse have to do with everything...?

Daniel.

 

[K.J.Healey]

yea, just write out AB=BA using B=[a,b;c,d] and A=[1,0;1,1]
and multiply out both sides.