三次函數的圖形
Author: 盧怡安

u = Vector((x(Corner[1]), 0), (x(Corner[3]), 0))
v = Vector((0, y(Corner[1])), (0, y(Corner[3])))
a = 0.2 (slider from -5 to 5, step 0.1)
b = -0.6 (slider from -5 to 5, step 0.1)
c = -3.8 (slider from -9 to 5, step 0.1)
d = 0.4 (slider from -5 to 7, step 0.1)
f(x) = a * x^(3) + b * x^(2) + c * x + d
A, B = Extremum(f)
C = TurningPoint(f)
text1: "$ 當x=" + (LaTeX[x(A)]) + " 時有極值" + (LaTeX[y(A)]) + "$"
text2: "$ 當x=" + (LaTeX[x(B)]) + "時有極值" + (LaTeX[y(B)]) + " $"