3. (30 pts) (Problem 9.12): Given the system of equations 2 x_{1}+x_{2}-x_{3}=1 5 x_{1}+2 x_{2}+2 x_{3}=-4 3 x_{1}+x_{2}+x_{3}=5 a) Use graphical method to estimate the solution; b) Write a MATLAB

function using Gauss-Jordan elimination to solve for x1, X2, and x3; c) Check your answer using the 'check' function you wrote in problem 2.e to verify the solution; d) If equation (1) and (2) remain the same, but equation (3) is changed to 2.5x +x2 + x3 = 5, write the equations into the format of Ax = b, calculate the determinant of matrix A using the function you wrote in problem 1.c, and discuss the solution of the new system of equations. e) If equation (1) and (2) remain the same, but equation (3) is changed to 3x1 + x2 + 3x3 = -5, write the equations into the format of Ax = b, calculate the determinant of matrix A using the function you wrote in problem 1.c, and discuss the solution of the new system of equations.