If A B and C are 3 times 3 3 times 7 and 7 times 9 matrices

If A, B, and C are 3 times 3, 3 times 7, and 7 times 9 matrices respectively, determine which of the following products are defined. For those defined, enter the size of the resulting matrix (e.g. \"3 times 4\", with spaces between numbers and \"x\"). For those undefined, enter \"undefined\". CB: BC: BA: A^2:

Solution

A = 3x3
B = 3 x 7
C = 7 x 9

CB :
C = 7 x 9
B = 3 x 7
CB
So, is the columns of C = rows of B?
No, they are not
Undefined ---> ANSWER

BC :
B = 3 x 7
C = 7 x 9
Defined
Enter \"3 x 9\" ---> ANSWER

BA :
B = 3 x 7
A = 3 x 3
Is columns of B = rows of A?
Nope
So, undefined

A^2 :
A^2 = A x A
A = 3 x 3
A = 3 x 3
DEfined obviously
Enter \"3 x 3\"----> ANSWER