Start from the four equations xi+1+2ari-xi-1 = i for i = 1,2, 3,4, with ro 5 0. write those equations in their matrix form ax b, then construct the corresponding augmented matrix [a | b], and using elementary row operations find the corresponding (a) (4p) row-echelon matrix, and (b) (4p) reduced-echelon matrix write down the solution of the system of equations from the reduced-echelon matrix