#054

import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(-3, 3, 600)
constants = [-4, -2, -1, 1, 2, 4]

fig, ax = plt.subplots(figsize=(7, 4.5))

for constant in constants:
    y = constant * np.exp(x) - 4
    y = np.where(np.abs(y) <= 10, y, np.nan)
    ax.plot(x, y, linewidth=2, label=f"C = {constant}")

ax.axhline(-4, color="black", linewidth=1, alpha=0.7, label="equilibrium y = -4")
ax.axvline(0, color="#111827", linewidth=0.8, alpha=0.35)
ax.set_title("Entry #054: y' = y + 4")
ax.set_xlabel("x")
ax.set_ylabel("y")
ax.set_ylim(-10, 6)
ax.grid(True, alpha=0.3)
ax.legend(fontsize=8, ncols=2)

fig.tight_layout()
plt.show()