Question 936213
formula: mid point( x,y) =((x1+x2)/2,(y1+y2)/2)
      midpoint( x,y)=(5,-11)
  one point(x1,y1)= (3,5)
       (5,-11)= ((3+x2)/2,(5+y2)/2)
      {{{ 5 = (3+x2)/2}}}      {{{ -11 = (5+y2)/2}}}
           5*2 = 3+x2              -11*2 =5+y2
             10=3+x2               -22=5+y2
            10-3=x2                    -22-5=y2
              7=x2                  -27=y2
 hence other end point(x2,y2)=(7,-27)