Find a basis of the row space of the matrix $$A = \left[\begin{array}{cccc} -3 &1 &3 &3\cr -3 &1 &3 &3\cr 0 &-3 &4 &4 \end{array}\right].$$
Basis: $\big\lbrace$ $\left[\Rule{0pt}{1.2em}{0pt}\right.$$\left]\Rule{0pt}{1.2em}{0pt}\right.$, $\left[\Rule{0pt}{1.2em}{0pt}\right.$$\left]\Rule{0pt}{1.2em}{0pt}\right.$ $\big\rbrace.$