Adjoint and Inverse of Matrices
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Matrix and Determinant

78798 If \(\omega\) is a complex cube root of unity and \(\mathbf{A}=\left[\begin{array}{cc}\omega & 0 \\ 0 & \omega\end{array}\right]\), then \(\mathrm{A}^{-1}=\)

1 \(-\mathrm{A}\)
2 \(2 \mathrm{~A}\)
3 \(\mathrm{A}^{2}\)
4 A
Matrix and Determinant

78799 If \(A=\left[\begin{array}{cc}1+2 i & i \\ -i & 1-2 i\end{array}\right]\) where \(i=\sqrt{-1}\) then \(A\) \((\operatorname{adj} \mathbf{A})=\)

1 \(-2 \mathrm{I}\)
2 \(2 \mathrm{I}\)
3 \(4 \mathrm{I}\)
4 \(5 \mathrm{I}\)
Matrix and Determinant

78800 If \(A\) is non-singular matrix and \((A+I)(A-I)\) \(=\mathbf{0}\), then \(\mathbf{A}+\mathbf{A}^{-1}=\)

1 I
2 \(2 \mathrm{~A}\)
3 0
4 \(3 \mathrm{I}\)
Matrix and Determinant

78801 If \(A=\left[\begin{array}{ll}x & 1 \\ 1 & 0\end{array}\right]\) and \(A=A^{-1}\), then \(x=\)

1 2
2 1
3 \(4\)
4 \(0\)
Matrix and Determinant

78798 If \(\omega\) is a complex cube root of unity and \(\mathbf{A}=\left[\begin{array}{cc}\omega & 0 \\ 0 & \omega\end{array}\right]\), then \(\mathrm{A}^{-1}=\)

1 \(-\mathrm{A}\)
2 \(2 \mathrm{~A}\)
3 \(\mathrm{A}^{2}\)
4 A
Matrix and Determinant

78799 If \(A=\left[\begin{array}{cc}1+2 i & i \\ -i & 1-2 i\end{array}\right]\) where \(i=\sqrt{-1}\) then \(A\) \((\operatorname{adj} \mathbf{A})=\)

1 \(-2 \mathrm{I}\)
2 \(2 \mathrm{I}\)
3 \(4 \mathrm{I}\)
4 \(5 \mathrm{I}\)
Matrix and Determinant

78800 If \(A\) is non-singular matrix and \((A+I)(A-I)\) \(=\mathbf{0}\), then \(\mathbf{A}+\mathbf{A}^{-1}=\)

1 I
2 \(2 \mathrm{~A}\)
3 0
4 \(3 \mathrm{I}\)
Matrix and Determinant

78801 If \(A=\left[\begin{array}{ll}x & 1 \\ 1 & 0\end{array}\right]\) and \(A=A^{-1}\), then \(x=\)

1 2
2 1
3 \(4\)
4 \(0\)
Matrix and Determinant

78798 If \(\omega\) is a complex cube root of unity and \(\mathbf{A}=\left[\begin{array}{cc}\omega & 0 \\ 0 & \omega\end{array}\right]\), then \(\mathrm{A}^{-1}=\)

1 \(-\mathrm{A}\)
2 \(2 \mathrm{~A}\)
3 \(\mathrm{A}^{2}\)
4 A
Matrix and Determinant

78799 If \(A=\left[\begin{array}{cc}1+2 i & i \\ -i & 1-2 i\end{array}\right]\) where \(i=\sqrt{-1}\) then \(A\) \((\operatorname{adj} \mathbf{A})=\)

1 \(-2 \mathrm{I}\)
2 \(2 \mathrm{I}\)
3 \(4 \mathrm{I}\)
4 \(5 \mathrm{I}\)
Matrix and Determinant

78800 If \(A\) is non-singular matrix and \((A+I)(A-I)\) \(=\mathbf{0}\), then \(\mathbf{A}+\mathbf{A}^{-1}=\)

1 I
2 \(2 \mathrm{~A}\)
3 0
4 \(3 \mathrm{I}\)
Matrix and Determinant

78801 If \(A=\left[\begin{array}{ll}x & 1 \\ 1 & 0\end{array}\right]\) and \(A=A^{-1}\), then \(x=\)

1 2
2 1
3 \(4\)
4 \(0\)
Matrix and Determinant

78798 If \(\omega\) is a complex cube root of unity and \(\mathbf{A}=\left[\begin{array}{cc}\omega & 0 \\ 0 & \omega\end{array}\right]\), then \(\mathrm{A}^{-1}=\)

1 \(-\mathrm{A}\)
2 \(2 \mathrm{~A}\)
3 \(\mathrm{A}^{2}\)
4 A
Matrix and Determinant

78799 If \(A=\left[\begin{array}{cc}1+2 i & i \\ -i & 1-2 i\end{array}\right]\) where \(i=\sqrt{-1}\) then \(A\) \((\operatorname{adj} \mathbf{A})=\)

1 \(-2 \mathrm{I}\)
2 \(2 \mathrm{I}\)
3 \(4 \mathrm{I}\)
4 \(5 \mathrm{I}\)
Matrix and Determinant

78800 If \(A\) is non-singular matrix and \((A+I)(A-I)\) \(=\mathbf{0}\), then \(\mathbf{A}+\mathbf{A}^{-1}=\)

1 I
2 \(2 \mathrm{~A}\)
3 0
4 \(3 \mathrm{I}\)
Matrix and Determinant

78801 If \(A=\left[\begin{array}{ll}x & 1 \\ 1 & 0\end{array}\right]\) and \(A=A^{-1}\), then \(x=\)

1 2
2 1
3 \(4\)
4 \(0\)