Question

I need this by tomorrow night 3/15/17

Answer 1

Well, surely you know what the picture below shows

the perimeter is 2l + 5w

and we know the perimeter is 750$\bf 750=2l+5w\implies \cfrac{750-5w}{2}=l \\\\\\ A(w)=\left( \cfrac{750-5w}{2} \right)w\implies A(w)= \cfrac{750w-5w^2}{2}$

now as for the part b)   $\bf \cfrac{dA}{dw}=375-5w\implies 0=375-5w\implies 75=w$

now.. if you run a first-derivative test on the critical point of 75

say, test hmmm 74.99999 and 75.00001

you'll notice the point is a maximum