# Thread: MATRIX problem: Help needed

1. ## MATRIX problem: Help needed

Hi,

Pls help to pricved solution of the below problem.

Consider the following 3 matrices:

2 12 18
13 15 20
19 17 1

12 2 1
13 14 21
9 18 7

12 2 7
30 18 22
9 16 4

Find --> (inverse of A i.e A-1) x (B x – C)

Please mail me the solution on lalitchugh@yahoo.com

Best Regards
Lalit Chugh

2. Originally Posted by lalitchugh
Hi,

Pls help to pricved solution of the below problem.

Consider the following 3 matrices:

2 12 18
13 15 20
19 17 1

12 2 1
13 14 21
9 18 7

12 2 7
30 18 22
9 16 4

Find --> (inverse of A i.e A-1) x (B x – C)
$\displaystyle A^{-1} B (-C)\approx \left[ \begin{array}{ccc} -51.6&-54.6&-32.5\\ 16.9&35.7&8.2\\ -17.4&-21.9&-9.2 \end{array} \right]$

Please mail me the solution on lalitchugh@yahoo.com
No.

RonL

3. Originally Posted by CaptainBlack
$\displaystyle A^{-1} B (-C)\approx \left[ \begin{array}{ccc} -51.6&-54.6&-32.5\\ 16.9&35.7&8.2\\ -17.4&-21.9&-9.2 \end{array} \right]$

No.

RonL
Or to be precise:

$\displaystyle \frac{1}{2602} \left [ \begin{array}{ccc}-134355&-142196&-84492\\43995&92792&21298\\-45192&-57048&-23892\end{array} \right ]$

To expand on CaptainBlack's "no," please be aware that it is better for everyone on the site to have the solution posted here so someone else who wants to learn the process can do so and ask questions about it. If the solution is simply sent to your e-mail others will not benefit as well.

-Dan

4. Originally Posted by topsquark
Or to be precise:

$\displaystyle \frac{1}{2602} \left [ \begin{array}{ccc}-134355&-142196&-84492\\43995&92792&21298\\-45192&-57048&-23892\end{array} \right ]$

To expand on CaptainBlack's "no," please be aware that it is better for everyone on the site to have the solution posted here so someone else who wants to learn the process can do so and ask questions about it. If the solution is simply sent to your e-mail others will not benefit as well.

-Dan
I was trying to avoid being too helpfull

RonL

5. Originally Posted by CaptainBlack
I was trying to avoid being too helpfull

RonL
Oops!

-Dan

6. New Question about Gauss-Jordan split out from this thread into a thread of its own here

RonL

7. Hello, Lalit!

Who assigned this hideous problem . . . Torquemada?
. . (No one expects the Spanish Inquisition!)

Given: .$\displaystyle A = \begin{pmatrix}2&12&18\\13&15&20\\19&17&1\end{pmat rix}\;\;B = \begin{pmatrix}12&2&1\\13&14&21\\9&18&7\end{pmatri x}\;\;C = \begin{pmatrix}12&2&7\\30&18&22\\9 &16&4\end{pmatrix}$

Find: .$\displaystyle A^{-1} \times B \times (-C)$

Thanks to topsquark's work, all you have to do is:

. . $\displaystyle \frac{1}{2602}\begin{pmatrix}\text{-}134355&\text{-}142196&\text{-}84492\\43995&92792&21298\\\text{-}45192&\text{-}57048&\text{-}23892\end{pmatrix}\,\begin{pmatrix}12&2&1\\13&4&2 1\\9&18&7\end{pmatrix}$$\displaystyle \begin{pmatrix}\text{-}12&\text{-}2&\text{-}7\\\text{-}30&\text{-}18&\text{-}22\\\text{-}9&\text{-}16&\text{-}4\end{pmatrix}$

Good luck!