Working Backward with Midpoints
Sometimes you'll know the midpoint and need to find an unknown endpoint. This requires working the midpoint formula in reverse, which you can totally handle!
For example, if R(3,1) is the midpoint between (-1,4) and (h,k), we set up equations using our formula:
- 3 = −1+h/2 → multiply both sides by 2 → 6 = -1+h → h = 7
- 1 = 4+k/2 → multiply both sides by 2 → 2 = 4+k → k = -2
In geometric problems like rectangles and rhombuses, midpoints help us find missing vertices. For a rhombus QRSP with three known vertices Q(9,6), R(-2,4), and P(4,-4), we can find S(a,b) by recognizing that the diagonals of a rhombus bisect each other.
Remember: In any four-sided shape problem, drawing a quick sketch on your coordinate plane can help you visualize the solution before diving into calculations.