let a be a 4×5 matrix. if a1,a2, and a4 are linearly independent and a3=a1+3a2,a5=−2a1−a2+2a4 determine the reduced row echelon form of a. u= [ 1 0 −1 0 2 0 1 −3 0 1 0 0 0 1 0 0 0 0 0 −2