Geometry

Question Analysis:
Tests understanding of parallelogram properties in coordinate plane.

Key Concept Explanation:
In parallelograms, midpoints of diagonals coincide.

Step-by-Step Solution:
Calculate midpoint of QS:
((1 + 5)/2,(2 + 1)/2) = (3, 1.5)
Let T = (x,y). Midpoint of RT must be (3, 1.5):
((4+x)/2,(4+y)/2) = (3,1.5)
Solve:
(4 + x)/2 = 3 ⇒ x = 2
(4 + y)/2 = 1.5 ⇒ y = -1

Common Mista...