Question

if a diagonal matrix is commutative with every matrix of the same order,then it is necessarily a ______ matrix
a. zero matrix
b. unit matrix
c. scalar matrix
d. a symmetric matrix
the ans is c... please explain how?... @Mathematics

Answer 1

i need explanation please... i have the key...

Answer 2

consider a general diagonal matrix to be A=[a 0,0,b] and other matrix B=[w x , y z] then compute AB then BA and then equate both which will you a=b which is a scalar matrix ....