Answer:



Step-by-step explanation:
Let
x----> the length of the rectangular garden
y---> the width of the rectangular garden
we know that
The perimeter of the rectangle is equal to

we have

so

simplify

------> equation A
Remember that the area of rectangle is equal to
----> equation B
substitute equation A in equation B
----> this is a vertical parabola open downward
The vertex is a maximum
The y-coordinate of the vertex is the maximum area
The x-coordinate of the vertex is the length side of the rectangle that maximize the area
using a graphing tool
The vertex is the point 
see the attached figure
so

Find the value of y

The garden is a square
the area is equal to
----> is equal to the y-coordinate of the vertex is correct
4x - 2x + 8 = 6(x + 4) Given
(4x - 2x) + 8 = 6(x + 4)
2x + 8 = 6(x + 4) Combine like terms
2x + 8 = (6)(x) + (6)(4)
2x + 8 = 6x + 24 Distributive Property
2x - 6x + 8 = 6x - 6x + 24
-4x + 8 = 24 Subtraction Property of Equality
-4x + 8 - 8 = 24 - 8
-4x = 16 Subtraction Property of Equality
-4x : (-4) = 16 : (-4)
x = -4 Division Property of Equality
Answer:
He will save 24 dollars.
Step-by-step explanation: