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