Question 829497
Exactly as you described.  You can represent a square composed of sides, a+b.  The lengths a and b can each be projected at right angles from each of this square's sides.  In this projective action, a and b from each side will sweep into these four areas:

a*a, b*b, and TWO of a*b.


The a*b may be a rectangle.  The a*a and b*b are both squares.  


All that is very easy to draw and label.  Seeing and understanding is also easier that way.



If you will do all that, you will also see why the Distributive Property of "Algebra 1, 2, and 3" work.