# Show that satisfies the equation x2 – 3A – 7 = 0. Thus, find A – 1.

A =

A2 =

=

Now, A2 – 3A – 7 = 0

=

=

=

So, A2 – 3A – 7I = 0

Multiply by A – 1 both sides

= A.A. A – 1 – 3A. A – 1 – 7I. A – 1 = 0

= A – 3I – 7A – 1 = 0

= 7A – 1 = A – 3I

= A – 1 =

Hence, A – 1 =

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