1. Factor the expression 16x^2 minus 72xy+81y^2 into a product of binomials

2. Factor the expression 81a^2 minus 36ab+4b^2 into a product of binomials.

3. Use the "difference of squares" rule to factor the following expression:
36-16y^2

4. The area of a rectangular athletic field is represented by the expression 12y^3+48y^2+24y square meters. Write an algebraic expression to represent one possible set of dimensions (in the sense "length times width") of the athletic field. Include correct units with your solution.