f(x) = (3 * x) + 1
A = Point(f)
B: (x(A), 0)
C: (0, y(A))
ε = 2.3 (slider from 0 to 3, step 0.05)
δ = 0.75 (slider from 0 to 1, step 0.05)
b: x = x(A) + δ
c: x = x(A) - δ
a: x = x(A)
d: y = y(A)
e: y = y(A) + ε
g: y = y(A) - ε