Question

A is a 2 ×2 matrix and 3(A+I)=I. Enter det(A+I).

Answer 1

`3(\mathbf A+\mathbf I)=\mathbf I`

`\mathbf A+\mathbf I=\frac13\mathbf I`

`\implies \det(\mathbf A+I)=\det\left(\frac13\mathbf I\right)=\left(\frac13\right)^2=\frac19`