import math
import matplotlib.pyplot as plt

x = [i * 0.1 for i in range(1, 40)]  # 0を除外して1〜9.9まで
y = [((math.sqrt(8)*math.sqrt(i+(1/8)))-1)/2 for i in x]
z = [((i**2)+i)/2 for i in x]
plt.plot(x, y)
plt.plot(x, z)
plt.title("«(Σ{y}{r=0}r)=x y=?» The solution and «(Σ{y}{r=0}r)=x x=?» The solution of")
plt.xlabel("x")
plt.ylabel("y")
plt.grid(True)
plt.show()