How to solve for e1 and e2 using matrix methods

[Would]

Hello, This problem isn't for a homework equation of mine.. But I am going over the MIT open courseware for this class before I enter it. Could someone tell me the steps taken on the bottom part of this matrix to come to the results of e1 and e2? I am not very familiar with how to manipulate matrices.. I have uploaded a picture of the problem.. I am not even sure how to get from that top equation to the middle one. Any help is appreciated..

 

[LCKurtz]

Hello, This problem isn't for a homework equation of mine.. But I am going over the MIT open courseware for this class before I enter it. Could someone tell me the steps taken on the bottom part of this matrix to come to the results of e1 and e2? I am not very familiar with how to manipulate matrices.. I have uploaded a picture of the problem.. I am not even sure how to get from that top equation to the middle one. Any help is appreciated..

He has just multiplied both sides by the inverse of the conductivity matrix. Look here:

http://www.mathwords.com/i/inverse_of_a_matrix.htm