a = 1 (slider from -5 to 5, step 0.1)
b = 2 (slider from -5 to 5, step 0.1)
h(x) = 2 x * (2 - log(x))
f_1(x) = 2 x * (1 - log(x))
f(x) = a x * (b - log(x))