How to express the difference of perfect squares?

Question

First of all, in order to understand my question, type in http://www.teacherweb.com/ny/arlington/algebraproject/hf0.stm. Click on units 5 & 6 on the left side and then click U6 L7- Factoring the Difference of Perfect Squares. Scroll down and find question 29. It says, For both of the following diagrams, express the shaded area as the product of two binomials. As a 
start, first express the area as the difference of perfect squares. How do I do the problem? 

 

Answer 1

29 a) the shaded area is the difference between the area of the big square and the small one. x^2-y^2=(x-y)(x+y)

29 b) (4x)^2-(3y)^2=(4x-3y)(4x+3y)