二次函數(三)

# f(x)=y=-3x**2+12x-9 求y=0 x之解
import numpy as np
from sympy import Symbol,solve
x=Symbol("x")
f=Symbol("f")
f=-3*x**2+12*x-9
ans=solve(f,x)
print(ans)

# f(x)=y=-3x**2+12x-9 畫圖形
import numpy as np
from sympy import Symbol,solve
import matplotlib.pyplot as plt
x=Symbol("x")
f=Symbol("f")
f=-3*x**2+12*x-9
ans=solve(f,x)
print(ans)
def yAns(x):
    y=-3*x**2+12*x-9
    return y
x1=np.linspace(-1,5,100)
y1=yAns(x1)
plt.plot(x1,y1)
plt.grid()
plt.show()

# f(x)=y=-3x**2+12x-9 畫圖及y=0 x之兩點
import numpy as np
from sympy import Symbol,solve
import matplotlib.pyplot as plt
x=Symbol("x")
f=Symbol("f")
f=-3*x**2+12*x-9
ans=solve(f,x)
print(ans)
def yAns(x):
    y=-3*x**2+12*x-9
    return y
x1=np.linspace(-1,5,100)
y1=yAns(x1)
plt.plot(x1,y1)
plt.plot(ans[0],0,"-o")
plt.plot(ans[1],0,"-o")
plt.text(ans[0],-3,"("+str(ans[0])+","+str(0)+")")
plt.text((ans[1]-0.5),-3,"("+str(ans[1])+","+str(0)+")")
plt.grid()
plt.show()