282. Use matrix method to solve the following system of equations:
2x – y - z = 7      
3x + y – z = 7            
x + y – z = 3

The given equations are
2x – y – z = 7    ...(1)
3x + y – z = 7    ...(2)
x + y – z = 3    ...(3)
These equations can be written as
                     

or  
                        
              
Co-factors of the elements of first row of | A | are

i.e. 0,  2,  2 respectively
Co-factors of the elements of second row of | A | are

i.e. – 2, – 1, – 3 respectively
Co-factors of the elements of third row of | A | are

i.e.  2, 1, 5 respectively