Replying to Urgent math help

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