MATH TEAM PRIDE. lol
Okay, here's the information from your pdf file: (I changed variable a to variable x)
f(a) = Top Curve = -x + 1
f(b) = Bottom Curve
Integral of f(a) = 0.5 (It's a triangle with intercepts at (0,1) and (1,0). Area = 1/2 (b) * (h) = 1/2
GIVENS
A = area between f(a) and f(b) = 0.2335
B = area between f(b) and axis = 0.2665
(A + B should = 0.5 and they do)
Now, f(a) is a straight line. f(b) has intercepts (0,1) and (1,0) and HAS to be at least polynomial. F(b) cannot be straight line and there should be a polynomial solvable equation. Anything more should need more information, so it's logical to assume that polynomial is answer.
Therefore, we can assume that it, f(b) = ax^2 + bx + c with solutions at least at (0,1) and (1,0)
f(b) = ax^2 + bx + c WITH inserted x
1 = c (x = 0)
0 = a + b + c (x = 1)
Then, a + b = -1 and a = - b - 1 OR b = - a - 1
Obviously, we need MORE information. Well, we know that the integral of f(b) from 0 to 1 equals the area of B which is 0.2665.
f(b) = ax^2 + bx + 1 (we know c = 1 now)
f(b) = ax^2 - ax - x + 1
Integral of f(b) = (a/3)x^3 - (a/2)x^2 - (1/2)x^2 + x = 0.2665
From 0 to 1, (a/3) - (a/2) - (1/2) + 1 = 0.2665
-(a/6) + (1/2) = 0.2665, a = 1.401
b = -2.401
c = 1
Thus, f(b) = 1.401x^2 - 2.401x + 1 = (1.401)b^2 - (2.401)b + 1 (in your units)