Q19 of 74 Page 7

If , show that A2 – 5A + 7I = O. Hence, find A – 1.

A =


A2 =


=


Now, A2 – 5A + 7I =


=


=


So, A2 – 5A + 7I = 0


Multiply by A – 1 both sides


= A.A. A – 1 – 5A. A – 1 + 7I. A – 1 = 0


= A – 5I + 7 A – 1 = 0


= A – 1 =


= A – 1 =


= A – 1 =


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