Find the rank of A=[12−124−2−1−21]A = \begin{bmatrix} 1 & 2 & -1 \\ 2 & 4 & -2 \\ -1 & -2 & 1 \end{bmatrix}A=12−124−2−1−21
rank(A)=0\text{rank}(A) = 0rank(A)=0
rank(A)=1\text{rank}(A) = 1rank(A)=1
rank(A)=2\text{rank}(A) = 2rank(A)=2
rank(A)=3\text{rank}(A) = 3rank(A)=3