Question

Write an expression for the area of square 4 by combining the areas of the four triangles and the two squares.

Answer 1

The area of Square 4 is a2+2ab+b2

The area of Square 5 is 2ab+c2

Setting them equal to one another (a2+2ab+b2=2ab+c2) and simplifying yields that a2+b2=c2 (note that 2ab is what they have in common), which is Pythagoras' theorem.