help

hint: you use the mid-point formula. 

see this link for the formula: https://www.thoughtco.com/geometry-midpoint-formula-2312239

I will give the answer later

From 4 to 1   is -3    add another -3      for x = -2

From 5 to -2  is -7   add another -7              y = -9

another hint: If you are only given one endpoint and a midpoint, you know what the middle of the line segment is. Since the midpoint is half of what the line segment's length is, all you have to do is find the distance between the endpoint given and the midpoint, then add that coordinate to your midpoint and get your other endpoint.

good work guest. I was about to give the answer. 

Here's another way

Call the other endpoint  (x, y)

So  we have that

4 + x                        5  +   y             

_____   =   1          _______   =  -2                multiply both sides by  2

    2                             2

4 +  x   =  2              5  +  y   =  - 4

subtract 4                    subtract 5

from both sides           from both sides

x  = -2                       y =  -9

nice