We want to write an expression in factored form to represent the area of the blue section.
The length and width of the small rectangle are a and b, respectively. The area A_s of the blue section is ab.
A= w * l ⇒ A_s= a* b
b
Since the yellow region has a width of 3 units all the way around, the width and the length of the big rectangle are 6 units longer than those of the small rectangle.
w= a+6 & l = b+6
Therefore, (a+6)(b+6) represents the area A_b of the big rectangle.
A=w * l ⇒ A_b= ( a+6)( b+6)
c
The difference between the areas of the rectangles gives the area of the yellow region.
