Question 983317
You can pick ANY coordinate between  -5 and +4.  You are looking for any vertical line with x value between -5 and +4.  Your description suggests you want the line to be perpendicular to the x axis.  It is not described any more clearly than that.  You can choose the midpoint if you want.   {{{x=k}}} for any  {{{-5<=k<=4}}}.