f(x) = x^(2) - x + 1
a = 0 (slider from -5 to 5, step 1)
b = 2 (slider from -5 to 5, step 0.1)
n = 18 (slider from 1 to 200, step 1)
o = UpperSum(f, a, b, n)
u = LowerSum(f, a, b, n)