jmc

Question

A line segment has one endpoint at (3,9) and midpoint at (1,2). What is the sum of the coordinates of the other endpoint?

Accepted Answer

Let the other endpoint be (x, y). We know that 3 + x2 + 9 + y2 = 1 + 2 = 3. Thus, 12 + x + y = 6. It follows that x + y = -6.