Find the area of a triangle with vertices with coordinates (0,9) , (4,6), and (-1,12).

Just to clarify, i know i can use distance formula to solve it. But my teacher taught us this "trick", well not a trick but an alternate easier way to do it.
Algebra 2.

Question

Find the area of a triangle with vertices with coordinates (0,9) , (4,6), and (-1,12).

Just to clarify, i know i can use distance formula to solve it. But my teacher taught us this "trick", well not a trick but an alternate easier way to do it. 
Algebra 2.

anonymous · Answer

The way has to do with matrixes