IMP Yr. 3 Problem With FOIL and Vertexs

[mac128k1984]

I can't figure this problem out for the life of me. I understand the follow up problems, but can't figure out the two main problems. I'm hoping that someone can help me out here:

A. Show that the vertex form expression -2(x-125)^2 + 31,250 is equivalent to 500x-2x^2

and

B. X= the width of a rectangle with a perimeter 200, and find an expression for the area in terms of x

(second half)

Show that your expression in part a is equivalent to -(x-50)^2 + 2500

I would apprechiate any help someone can give on this. Thanks!

 

[stapel]

A) You've multiplied out "-2(x - 125)² + 31250", simplified, and... then what?

B) Are "X" and "x" related? If so, how? If the width is X and the perimeter is 200, then what must be the length? (Plug "X" into the perimeter formula for 'w", and solve for L in terms of X. Plug X and the expression for L into the area formula.)

Eliz.