 Solution

With $a=1$, $b=2$, $c=2$, substitute into the matrix equations. The equations reduce to $x+2z=0$ and $3y+z=0$, with the latter repeated. Taking $z=3t$ gives the complete null spaceThe two independent rows impose two constraints on three unknowns, leaving exactly one free parameter. This also includes the zero solution at $t=0$.