# [SOLVED] Matrix Operations

• Feb 13th 2010, 01:53 PM
Noxide
[SOLVED] Matrix Operations
I need some help with this. There's no answer in the back of the book and I computed the inverse to check my answer and I keep getting it wrong.

http://img706.imageshack.us/img706/4346/desklu.jpg
• Feb 14th 2010, 03:19 AM
HallsofIvy
"2 times row one of $A^{-1}$ minus row two of $A^{-1}$ plus 3 times row 3 of $A^{-1}$" is simply $\begin{bmatrix}2 & -1 & 3\end{bmatrix}A^{-1}$. But that is the second row of A. Multiplying the second row of A by $A^{-1}$ gives the second row of the identity matrix which is $\begin{bmatrix}0 & 1 & 0\end{bmatrix}$.
• Feb 14th 2010, 07:30 AM
Noxide
ah ok got it