Posted by **Katherine** on Tuesday, November 18, 2008 at 6:14pm.

find the values of a and b given that matrix A=

[a -4 -6]

[-8 5 7]

[-5 3 4]

is the inverse of matrix B =

[1 2 -2]

[3 b 1]

[-1 1 -3]

It would really help if you showed how you did it.

Thanks a lot!

- Math -
**Reiny**, Tuesday, November 18, 2008 at 8:23pm
I trust you know how to multiply two matrices

and I trust that you know that if you multiply any matrix by its inverse you get the identity matrix, namely

1 0 0

0 1 0

0 0 1

so using the first row of matrix A and the first column of matrix B you get

a - 12 + 6 = 1

a = 7

then second row of A by second column of B gives us

-16 + 5b + 7 = 1

b = 2

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