1. Consider the following system of equations. -x_{1}+9 x_{2}-2 x_{3}+4 x_{4}=0 2 x_{1}-18 x_{2}+x_{3}-2 x_{4}=-3 x_{1}-9 x_{2}+4 x_{3}-8 x_{4}=2 а.Row-reduce the augmented matrix of the system. (Order the columns from

x1 to x4) b. Identify the free variables from the row reduced matrix. (Circle the correct answer). a.X1 b. X2 С. Хз d. X4 Use back substitution to write the variables corresponding to the leading variables in terms of the free variables. State the resulting solution. (Fill in the blanks for t)C. \left.\left[\begin{array}{l} x_{1} \\ x_{2} \\ x_{3} \\ x_{4} \end{array}\right]=\left[\begin{array}{c} -2 \\ 0 \\ 1 \\ 0 \end{array}\right]+s\left[\begin{array}{l} 9 \\ 1 \\ 0 \\ 0 \end{array}\right]=t\right]