Final answer:
To factor the expression (x^2 - 25) ft^2, use the difference of squares formula and factor it as (x + 5) (x - 5) ft^2. The additional feet added to the length and subtracted from the width of the rectangular garden are both 5 ft. If the original length of the square garden is x ft, the final length of the rectangular garden is (x + 5) ft.
Step-by-step explanation:
a. To factor the expression (x^2 - 25) ft^2, we can use the difference of squares formula, which states that a^2 - b^2 can be factored as (a + b)(a - b). In this case, a = x and b = 5. So, the expression can be factored as (x + 5)(x - 5) ft^2.
b. Since the rectangular garden must have the same perimeter as the square garden, we can use the factored expression from part a to determine how many feet were added to the length and subtracted from the width. Since the length is represented by (x + 5) ft and the width is represented by (x - 5) ft, the additional feet added to the length and subtracted from the width are both 5 ft.
c. The original length of the square garden is x ft. Since Juanita added 5 ft to the length when she changed the design to a rectangle, the final length of the rectangular garden is (x + 5) ft.