Question

maximize A=xy if x+y=12

Answer 1

y=16-2x
so put that within the equation

A=x(16-2x)
A=16x-2x^2

taking the derivative of a you get

A'(x)=16-4x
when A'= 0 you get -16=-4x
4=x
if x = 4
y=16-2(4)= 8

x=4
y=8