Solve the following system of equations by matrix method:

3x + 4y + 7z = 14


2x – y + 3z = 4


X + 2y – 3z = 0

The given system can be written in matrix form as:


or A X = B


A = , X = and B =


Now, |A| = 3


= 3(3 – 6) – 4(– 6 – 3) + 7(4 + 1)


= – 9 + 36 + 35


= 62


So, the above system has a unique solution, given by


X = A – 1B


Cofactors of A are:


C11 = (– 1)1 + 1 3 – 6 = – 3


C21 = (– 1)2 + 1 – 12 – 14 = 26


C31 = (– 1)3 + 112 + 7 = 19


C12 = (– 1)1 + 2 – 6 – 3 = 9


C22 = (– 1)2 + 1 – 3 – 7 = – 10


C32 = (– 1)3 + 1 9 – 14 = 5


C13 = (– 1)1 + 2 4 + 1 = 5


C23 = (– 1)2 + 1 6 – 4 = – 2


C33 = (– 1)3 + 1 – 3 – 8 = – 11


adj A =


=


A – 1 =


Now, X = A – 1B =


X =


X =


X =


Hence, X = 1,Y = 1 and Z = 1


2