Question 1064005
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        Here I will explain you how to find quickly the area of triangle ABC 

        with the vertices at the integer grid points in a coordinate plane.



Draw the minimal rectangle on the grid which concludes the given triangle.
Identify the triangles on the grid inside this rectangle that are outside the given triangle.



It is quite easy to find the area of each such a triangle.


After that, you will find the area of your triangle ABC mentally, by subtraction
the areas of the three other triangles from the area of rectangle.



Notice that doing this way, You will find the PRECISE area of triangle ABC mentally and quickly,
without doing boring calculations.



It is the best strategy and the most valuable piece of knowledge, which you can learn from this problem.