Question 1109088
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A solution using the midpoint formula, as shown by the other tutor, is fine.<br>
But plugging numbers into formulas does not give you much mental exercise.  Instead, get some worthwhile brain exercise by solving the problem by logical reasoning.<br>
Imagine you are taking a trip from one endpoint of the line segment to the other.  When you reach the midpoint, you are halfway there; the part of the trip that remains is equal to the part you have finished.<br>
In getting from endpoint (-5,-5) to the midpoint (-10,-7), you have gone left 5 units (from -5 to -10) and down 2 units (from -5 to -7).  To get from the midpoint to the other endpoint, you need to go another 5 to the left and another 2 down.<br>
5 left from -10 is -15; 2 down from -7 is -9.
The other endpoint is (-15,-9).