Let the eigenvalues of the third order invertible matrix a be 1, 2 and 4 respectively, then [i-2a ^ - 1] is equal to It's the value of the determinant,

Let the eigenvalues of the third order invertible matrix a be 1, 2 and 4 respectively, then [i-2a ^ - 1] is equal to It's the value of the determinant,

The eigenvalues of i-2a ^ - 1 are (1-2 / λ): - 1, 0, 1 / 2
So its determinant is 0