Question

to do with Matrices:

i have this question:
c= a 3*3 matrix

but its asking:
show by direct multiplication that c inverse = (3*3 matrix)

see attached also

Answer 1

c= 1 2 1
1 1 2
1 3 -1

c^-1 = -7 5 3
3 -2 -1
2 -1 -1

Answer 2

i guesss my question is whats direct multiplication?

Answer 3

\[CC^{-1} = I\]
where I is the 3x3 Identity Matrix (ones on the diagonal, 0s everywhere else)

Answer 4

So you need to carry out the multiplication of matricies. Do you know how to multiply 2 matrices?

Answer 5

yes

Answer 6

thats what you want to do then. multiply the two matrices, and show that you get:
I = 1 0 0
0 1 0
0 0 1

Answer 7

oh, so i just had to remember that a matrix by its inverse is the identity matrix then show that with those two given..

thanks