If f(x) = x^2 -5x +7 and let A be a matrix . f(A) is written as A^2 -5A +7I where I is an Identity matrix .Why 7 is written as 7I as It is a scalar and multiplying by matrix makes it a matrix .

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Solution

It is a theorem.
You cannot add 7 to a matrix.You can add only 2 matrixes.So inorder to make 7 in a matrix form we multiply it with I

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