Urgent math help

[Mr_Orange]

this is due in an hour.... theres 2 questions I don't get

(c) A rectangle has its base lying on the x− axis and its upper corners on the parabola y=18−x2. If the upper right corner is (s

t), express the area A of the rectangle as a function of s.

Answer: The area of the rectangle is A=
AND...
(1 pt) For the function f(x)=x2+5x, simplify each expression as much as possible.
(f(w)-f(x)) / w-x =
(NOTE: x=/=w

 

[Arabian.]

I don't remember this at all.
I can tell you that the extra credit is sqrt(f(x) -5x)) = x
I do not, however, wish to look up the equation for solving the rectangle problem. I'm sure it's in your book and it's easier than it seems.

 

[Mr_Orange]

i'll try your answer if I cant figure it out and run out of time thanks...
can anyone find the domain of sqrt((3)((x-8)/x)+2) ???