1. A triangle has vertices $P,Q$ and $R$.

The coordinates of $P$ are (—3, —6)
The coordinates of $Q$ are (1, 4)
The coordinates of $R$ are (5, —2)

$M$ is the midpoint of $PQ$.
$N$ is the midpoint of $QR$.

Prove that $MN$ is parallel to $PR$.
You must show each stage of your working.