We have a segment CD, of which we know the midpoint M = (-1,-2) and one of the endpoints C = (4,3).
We have to find the coordinates of the other endpoint D.
We will use the fact that the coordinates x and y of the midpoint are the average of the coordinates x and y of the endpoints respectively.
Then, for the x-coordinates we can write:

Then, we can calculate the x-coordinate of D from the x-coordinates of C and M.
The same can be written for the y-coordinates:

Then, we can replace and calculate each coordinate of D as:


The coordinates of D are (-6,-7).
We can check with a graph as: