Combine polynomial functions

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import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
%matplotlib inline
plt.rcParams['font.size']=15

def plt_legend_out(frameon=True):
    plt.legend(bbox_to_anchor=(1.05, 1), loc='upper left', borderaxespad=0, frameon=frameon)

Linear expression

def f(x):
    return x

x = np.linspace(-10,10,100)

plt.plot(x,f(x))
plt.axvline(x=0,color='gray',lw=0.5)
plt.axhline(y=0,color='gray',lw=0.5)
plt.show()

Quadratic expression

def f(x):
    return -x**2

x = np.linspace(-10,10,100)

plt.plot(x,f(x))
plt.axvline(x=0,color='gray',lw=0.5)
plt.axhline(y=0,color='gray',lw=0.5)
plt.show()

Quadruple formula

def f(x):
    return x**4

x = np.linspace(-10,10,100)

plt.plot(x,f(x))
plt.axvline(x=0,color='gray',lw=0.5)
plt.axhline(y=0,color='gray',lw=0.5)
plt.show()

combination

def f(x):
    return 0.9*x**4 - (50*x**2) + 50*x + 200

x = np.linspace(-10,10,100)

plt.plot(x,f(x))
plt.axvline(x=0,color='gray',lw=0.5)
plt.axhline(y=0,color='gray',lw=0.5)
plt.show()