1. ## [SOLVED] Matrix Inverse

Solve the system using the inverse of the coefficient matrix of the equivalent matrix equation

2x+8y+6z=20
4x+2y-2z=-2
3x-y+z=11

Help!

Thanks

2. Originally Posted by ToXic01
Solve the system using the inverse of the coefficient matrix of the equivalent matrix equation

2x+8y+6z=20
4x+2y-2z=-2
3x-y+z=11

Help!

Thanks
What have you tried? Where are you stuck? Have you reviewed similar examples in your class notes and textbook?

3. similar examples skipped steps I still need help
thanks

4. Originally Posted by ToXic01
similar examples skipped steps I still need help

thanks
What steps do the examples in your notes apparently skip?

$\displaystyle AX = B \Rightarrow X = A^{-1}B$.

Now... please say exactly where you're stuck. Getting A? Finding $\displaystyle A^{-1}$ ? Multiplying $\displaystyle A^{-1}B$ ?

5. 1 0 0 0 -1/2 1
0 1 0 1/14 5/7 -1
0 0 1 1/14 -11/14 1
the answer is not the same as the question

6. Originally Posted by ToXic01
1 0 0 0 -1/2 1
0 1 0 1/14 5/7 -1
0 0 1 1/14 -11/14 1
the answer is not the same as the question

Apparently you mean that $\displaystyle A^{-1}=\begin{pmatrix}0&\!\!\!-1\slash 2&1\\1\slash 14&5\slash 7&\!\!\!-1\\1\slash 14&\!\!\!-11\slash 14&1\end{pmatrix}$ . This is, of course, wrong...and I write "of course" because if you multiply this by $\displaystyle A$ you do not get the

identity matrix, so it shouldn't be a surprise that your answer doesn't match the actual one.

You have the first column correct, but all the other entries are wrong, so...do it again, this time more carefully!

Tonio

7. i re-did it again and got the answer thanks