Final answer:
The area of a rectangular garden with a length of 4p+18 feet and a width of 4p feet is expressed as the product of these two dimensions, which simplifies to 16p² + 72p square feet, corresponding to option (a).
Step-by-step explanation:
The area of a rectangle is given by the formula length × width. For the rectangular garden described in the question, with a length of 4p+18 feet and a width of 4p feet, the expression for the area in square feet can be found by multiplying these two dimensions:
Area = length × width
Area = (4p+18) × (4p)
Area = 4p × 4p + 4p × 18
Area = 16p² + 72p
So the correct expression for the area of the garden is 16p² + 72p, which corresponds to option (a).