Science:Math Exam Resources/Courses/MATH152/April 2013/Question B 03 (a)/Statement

Let A be a certain $2\times 3$ matrix. Suppose that using elementary row operations, the matrix A can be transformed into the matrix

$U=\left[\begin{array}{ccc}1& 0& -7\\ 0& 1& 4\end{array}\right]$

Find all solutions, if any, of the system $Ax=0$