Puzzle 1. The solution is shown in the left diagram. The
approach can be described as "folding" of the frame. Folding three
matchsticks (shown as black) inside the square reduces its area by two
square units - the shaded right triangle equals the area of one square unit.
Puzzle 2. The solution starts the same is in Puzzle 1 but then
two matchsticks are "unfolded" back in order to add one square unit back to
the shape - see the right diagram.
