cv4_geometricky-vyznam-derivace

a = -0.997 (slider from -1 to 4)
f(x) = ((3 * x) - 1) / ((2 * x) + 3)
S1: (a, f(a))
S2: (-1, f(-1))
g = Line(S1, S2)
k: (f(a) - f(-1)) / (a + 1)