Consider the matrix A=(2412)A = \begin{pmatrix} 2 & 4 \\ 1 & 2 \end{pmatrix}A=(2142). Which statements are true?
AAA is invertible because it is 2×22 \times 22×2
AAA is singular (not invertible) because det(A)=0\text{det}(A) = 0det(A)=0
A−1=(12−2−141)A^{-1} = \begin{pmatrix} \frac{1}{2} & -2 \\ -\frac{1}{4} & 1 \end{pmatrix}A−1=(21−41−21)
The first row is a scalar multiple of the second row, so rows are linearly dependent