多項式(21)
Author: 藍邦偉　老師

(A)x²+2x=(x+1)²-1≥-1

(B)x²-2x+2=(x-1)²+1≥1>0

(C)x²+4x+9=(x+2)²+5≥5>0

(D),(E)首項為負，不可能恆正

n = 0 (slider from 0 to 5, step 1)
A = (-1.64, -0.3)
B: A + (1.4, 0)
D: A + (0, 0.6)
C: B + D - A
poly1, a, b, c, d = Polygon(A, B, C, D)