Calculate the area of a rectangle specified on the plane by points with coordinates A (3; 6), B (-2; -6), C (-2; -4), D (3; -4)

First, you need to build this quadrangle on the coordinate axis (this is not a rectangle) by points. One cell can be taken as a unit segment. Then connect the points with lines – we get the sides of the quadrangle. Then divide this quadrilateral into two right-angled triangles and calculate their areas as half the product of the legs. Then just add the two areas of the triangles and get the area of the quadrangle.
Answer: 30.