If M(31, –5) is the midpoint of the line segment whose endpoints are A and B(2, –19), what are the coordinates of endpoint A?

The midpoint coordinates are the averages of the endpoints’ corresponding coordinates. So endpoint A must satisfy x = 2(31) − 2 = 60 and y = 2(−5) − (−19) = 9. Therefore, A is (60, 9), choice D.

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