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If A=[10−17]A = \begin{bmatrix} 1 & 0 \\ -1 & 7 \end{bmatrix} is a matrix such that A2=8A+KIA^2 = 8A + KI,where II is an identity matrix of order 2 then value of KK is :

Solution

✅ Correct Option: 3

A2=[10−849]A^2 = \begin{bmatrix}1&0\\-8&49\end{bmatrix} and 8A=[80−856]8A = \begin{bmatrix}8&0\\-8&56\end{bmatrix}.

Subtracting, A2−8A=[−700−7]=−7IA^2-8A = \begin{bmatrix}-7&0\\0&-7\end{bmatrix} = -7I.

Hence K=−7K = -7.

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