Question 1079235
The midpoint is the average of the x and y values. 
So let the other endpoint be (x,y),
Endpoint (5,6), Midpoint (2,-4)
x:{{{(5+x)/2=2}}}
{{{5+x=4}}}
{{{x=-1}}}
and
y:{{{(6+y)/2=-4}}}
{{{6+y=-8}}}
{{{y=-14}}}
(-1,-14)
Do the remaining ones the same way.