Mowing a Field A square field in a certain state park is mowed around the edges every week. The rest of the field is kept unmowed to serve as a habitat for birds and small animals (see the figure). The field measures b feet by b feet, and the mowed strip is x feet wide (a) Explain why the area of the mowed portion is b2 - (b 2x)2 (b) Factor the expression in part (a) to show that the area of the mowed portion is also 4x(b x) b.