If show that A2 –5A + 7I = 0. Use this to find A4.
Given:
I is identity matrix so
To show that
Now, we will find the matrix for A2, we get
[as cij = ai1b1j + ai2b2j + … + ainbnj]
Now, we will find the matrix for 5A, we get
So,
Substitute corresponding values from eqn(i) and (ii), we get
[as rij = aij + bij + cij]
Therefore,
Hence proved
We will find A4
Multiply both sides by A2, we get
As multiplying by the identity matrix, I don’t change anything. Now will substitute the corresponding values we get
Hence this is the value of A4