import numpy as np
import matplotlib.pyplot as plt
%matplotlib inline

arr=np.array([[-1,1,2,-1,2],
             [9,-1,-6,5,6]])
arr=np.vstack([arr,[2,-1,2,1,0]])
arr[0]+=arr[1]
arr[2]-=arr[1]
arr[1]=arr[1]*5-arr[0]

# Строим графики

plt.plot(x, y1, label=r'$y\geqslant2$')
plt.plot(x, y2, label=r'$2y\leq25-x$')
plt.plot(x, y3, label=r'$4y\geq 2x - 8$')
plt.plot(x, y4, label=r'$y\leq 2x-5$')
plt.xlim((0, 16))
plt.ylim((0, 11))
plt.xlabel(r'$x$')
plt.ylabel(r'$y$')

# Закрашиваем область допустимых планов

y5 = np.minimum(y2, y4)
y6 = np.maximum(y1, y3)

plt.fill_between(x, y5, y6, where=y5>y6, color='grey', alpha=0.5)
plt.legend(bbox_to_anchor=(1.05, 1), loc=2, borderaxespad=0.)