21. Exemplar Example Problem VI

The mid-points $D$, $E$, $F$ of the sides of a triangle $ABC$ are $(3,4)$, $(8,9)$ and $(6  , 7 )$ . Find the coordinates of the vertices of the triangle.

 

 

The coordinates of $A$ is $($, $)$

 

The coordinates of $B$ is $($, $)$

 

The coordinates of $C$ is $($, $)$