Answer: PQ ∥ RS and QR ∥ SP, so □PQRS is a parallelogram.
Slope \(=\dfrac{y_2-y_1}{x_2-x_1}\).
Slope of PQ \(=\dfrac{2+2}{5-1}=1\); slope of RS \(=\dfrac{-5+1}{-1-3}=1\).
Slope of QR \(=\dfrac{-1-2}{3-5}=\dfrac32\); slope of SP \(=\dfrac{-2+5}{1+1}=\dfrac32\).
Both pairs of opposite sides are parallel, so PQRS is a parallelogram.