If A = 
find x and y such A2 – xA + yI = O. Hence, evaluate A – 1.
A = 
A2 = 
= 
Now, A2 – xA + yI = 
= 22 – 4x + y = 0 or 4x – y = 22
= 18 – 2x = 0 or X = 9
= Y = 14
So, A2 – 5A + 7I = 0
Multiply by A – 1 both sides
= A.A. A – 1 – 9A. A – 1 + 14I. A – 1 = 0
= A – 9I + 14 A – 1 = 0
= A – 1 = 
= A – 1 = 
= A – 1 = 
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