1. Earlier, a reading question asked you to solve the system of equations \begin{align*} 2x_1 + 3x_2 - x_3&= 0\\ x_1 + 2x_2 + x_3&= 3\\ x_1 + 3x_2 + 3x_3&= 7 \end{align*} Use a linear combination to rewrite this system of equations as a vector equality.
  2. Find a linear combination of the vectors \begin{equation*} S=\set{\colvector{1\\3\\-1},\,\colvector{2\\0\\4},\,\colvector{-1\\3\\-5}} \end{equation*} that equals the vector $\colvector{1\\-9\\11}$.
  3. The matrix below is the augmented matrix of a system of equations, row-reduced to reduced row-echelon form. Write the vector form of the solutions to the system. \begin{equation*} \begin{bmatrix} \leading{1}&3&0&6&0&9\\ 0&0&\leading{1}&-2&0&-8\\ 0&0&0&0&\leading{1}&3 \end{bmatrix} \end{equation*}