Q. Three concurrent lines are drawn from vertices $A (1,2), B (2,3)$ and $C (3,7)$ of $\triangle ABC$ which divide the triangle into 6 parts having equal areas and point of concurrency is point $O$. Let $P(-5,4)$ and $Q(-3,7)$ be two points such that orthocentre of $\triangle O P Q$ be point $R$. If orthocentre of $\triangle P Q R$ be $( a , b )$, then find $a + b$.
Straight Lines
Solution: