Question 31028
What must be true about  x, y, z and w  if  AB = BA for the matrices

A= 
x  y
z  w

B=
1  1
-1  1
------------------------------------------------
AB=
X-Y,X+Y
Z-W,Z+W
	
BA=
X+Z,Y+W	
-X+Z,-Y+W	
	
AB=BA....HENCE

X-Y=X+Z............OR	Y=-Z
X+Y=Y+W............OR	X=W
Z-W=-X+Z........OR	X=W
Z+W=-Y+W.........OR	Y=-Z

HENCE WE SHOULD HAVE......X=W AND Y=-Z