Help! i I can not do inverse matrix by hand! can anyone give me tips? thanks!

Question

anonymous · Answer

What are the dimensions of the matrix?

anonymous · Answer

3x3 - 1st row 4 2 2  2nd row 4 2 0 3rd row 5 0 5

anonymous · Answer

$$\left[\begin{matrix}4 & 2 & 2 \4 & 2 & 0\ 5 & 0 & 5\end{matrix}\right]$$
Do you know how to take the determinant of a two-by-two matrix?

anonymous · Answer

I guess not.

anonymous · Answer

I was asking to check. I can help you. If you have a two-by-two:$$\left[\begin{matrix}a & b \ c & d\end{matrix}\right]$$
The determinant of the matrix is:$$a*d-b*c$$

anonymous · Answer

I can do a 2x2 determinent. Actually not sure how to do an inverse on a 2x2 either :-)

anonymous · Answer

I realize now that I was about to get you the determinant of the three-by-three and not the inverse...
It's difficult to inverse high-order matrices, do you know how to row-reduce?

anonymous · Answer

I know you have to find the identity using gauss-jordan, but I don't know how they keep finding the inverse from that.

anonymous · Answer

I have no idea what gauss-jordan is.$$\left[\begin{matrix}-1/2 & 1/2 & 1/5 \1&-1/2&-2/5\ 1/2 & -1/2&0\end{matrix}\right]$$
I found that using wolfram alpha.

anonymous · Answer

THANKS FOR YOUR HELP. SORRY I DIDN'T REPLY SOONER, AT WORK AND PHONE WENT CRAZY.

anonymous · Answer

Don't worry about it :)