Area of the rectangle is given as = 16 square inches
We know
Length * width = Area
Then
Width = Area/Length
Now
Perimeter = 2 (Length + Width)
Perimeter = 2[ {Length + (Area/Length)}]
Perimeter = 2[Length + (16/Length)]
When d(Perimeter)/d(length) = 0,
Then
2[Length + (16/Length)] = 0
Length + (16/Length) = 0
Length^2 + 16 = 0
(Length)^2 = -(4)^2
Then
Length = 4 inches
Now
Width = Area/Length
= 16/4
= 4 inches.
