(b) The given system of homogeneous equations has
$\Delta = \left| {\,\begin{array}{*{20}{c}}1&{\,\,4}&{ - 1}\\3&{ - 4}&{ - 1}\\1&{ - 3}&{\,\,\,1}\end{array}} \right| = 1( - 4 - 3) - 4(3 + 1) - 1( - 9 + 4)$
$ = - 7 - 16 + 5 \ne 0$.
There exists only one trivial solution.