a_1 = 2 (slider from 0 to 20, step 0.1)
f_2(x) = 1 / 4 x^(3) - a_1 x^(2) + a_1^(2) x
a_2 = 3 (slider from 0 to 20, step 0.1)
f_3(x) = 1 / 4 x^(3) - a_2 x^(2) + a_2^(2) x