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
The answer is 2,-1,4
Help!
Thanks
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