f(x) = 1 / 16 x^(4) - 1 / 4 x^(3) - 1
A = Point(f)
m: f'(x(A))
a = Tangent(A, f)
g(x) = f'(x)
B = (1, 5)
C = (1, 3)
D = (4, 3)
E = (4, 5)
poly1, b, c, d, e = Polygon(B, C, D, E)
text2: "f '(x_o) = " + m
text1: "x_o = " + (x(A))