Given just this diagram, I am trying to find the dimensions which gives the maximum area.
I understand that I have to apply the first derivative test for local extrema, which involves setting the first derivative of a function equal to $0$ to find the critical points of the function which could be a local/absolute maxima/minima. We then use the second derivative test to confirm whether the second derivative is less than 0 in the domain of the function and if it aligns, means it is the maximum dimensions.
The perimeter of the rectangle is: $P = 2h + 2w$
with no other information given, how do I express the an expression as a function of 1 variable so that I can perform the first and second derivative test?