Acomposite figure is formed by combining a square and a triangle its total area is 32.5 ft2 the area of the triangle is 7.5 ft2 what is the length of each side of the square

Area of square = Composite Area - Area of Triangle

                          =    32.5  - 7.5  = 25

Area of square = 25 square feet.

Formula for area of square = s²

s²  = 25

s = √25

s = 5

Length of each side of square = 5 feet.

Answers are
a) the area of a square is A = L^2= 16x^2 - 8x+1= (4x  -1)^2, so                    sqrt (L^2)= sqrt (4x  -1)^2, and so L = 4x - 1,  
b) the area of a rectangle is A = h x w = 81x^2-4y^2 = (9x- 2y) (9x + 2y)
so w =  (9x- 2y)  and h=(9x + 2y)
c) let be f(x) = x^3-9x^2-4x+36, so f(2) = 8-36-8+36=0, f(x) can be written as 
f(x) = (x - 2) (ax^2 + bx +c), we must find a, b and c
(ax^2 + bx +c)=x^3-9x^2-4x+36  / x - 2, after the division we have
ax^2 + bx +c = x^2-7x-18, and x= - 2 is a zero of x^2-7x-18, so x^2-7x-18 = (x +2) (ax + b), ax + b =x^2-7x-18  / x + 2 = x - 9

finally V = h x w x L =(x - 2)  (x +2) (x - 9),