If the line joining the points $(-1,2,3),(2,-1,4)$ is perpendicular to the line joining the points  $(x,-2,4),(1,2,3)$ then $x=$

D.r’s of the line joining $(-1,2,3),(2,-1,4)$ are $\left(3,-3,1\right)$
D.r’s of the line joining  $(x,-2,4),(1,2,3)$ are $(1-x,4,-1)$
The two lines are perpendicular  $\Rightarrow 3(1-x)-12-1=0$, $\Rightarrow x=-\frac{10}{3}$