import matplotlib.pyplot as plt
import numpy as np

# Function calculating f(x):
def f(x):
    return (x - 1)**2 + 3

# Function calculating dfdx with central difference:
def dfdx(f_vec, h):
    deriverte = np.zeros(len(f_vec)) + np.nan
    for i in range(1, len(f_vec)-1, 1):
        deriverte[i] = (f_vec[i+1] - f_vec[i-1])/(2*h)
    return deriverte 

dx = 0.001
x_start = 0.0
x_stop = 3.0
N = int (( x_stop - x_start )/ dx + 1)
x_koor = np.linspace(x_start, x_stop, N)

f_func = f(x_koor)
f_derivert = dfdx(f_func, dx)

for i in range(0, len(f_derivert) - 1, 1):

    if f_derivert[i]*f_derivert[i+1] <= 0:
       print(round(x_koor[i], 2), round(f(x_koor[i]),2))