# Solving for x in a matrix

• Apr 5th 2012, 05:43 AM
youngb11
Solving for x in a matrix
Solve the following equation for x

| x a x b |
| b x a x | = 0
| x b x a |
| a x b x |

(Determinant equals zero). I'm not sure how to do this and any help would be appreciated!
• Apr 5th 2012, 05:57 AM
Prove It
Re: Solving for x in a matrix
Quote:

Originally Posted by youngb11
Solve the following equation for x

| x a x b |
| b x a x | = 0
| x b x a |
| a x b x |

(Determinant equals zero). I'm not sure how to do this and any help would be appreciated!

Do you know how to evaluate a 4x4 determinant?

\displaystyle \begin{align*} \left|\begin{matrix} x & a & x & b \\ b & x & a & x \\ x & b & x & a \\ a & x & b & x \end{matrix}\right| &= x \left|\begin{matrix} x & a & x \\ b & x & a \\ x & b & x\end{matrix}\right| - a\left| \begin{matrix} b & a & x \\ x & x & a \\ a & b & x \end{matrix}\right| + x\left|\begin{matrix} b & x & x \\ x & b & a \\ a & x & x \end{matrix}\right| - b\left|\begin{matrix} b & x & a \\ x & b & x \\ a & x & b \end{matrix}\right| \end{align*}

Can you evaluate each of these 3 x 3 determinants?
• Apr 5th 2012, 06:44 AM
youngb11
Re: Solving for x in a matrix
Before I continue with the rather length process, isn't there still the problem of 3 variables with only 1 equation?
• Apr 5th 2012, 07:04 AM
a tutor
Re: Solving for x in a matrix