diff --git a/calculus-derivatives-with-python.ipynb b/calculus-derivatives-with-python.ipynb
index bfffcaa..65061cf 100644
--- a/calculus-derivatives-with-python.ipynb
+++ b/calculus-derivatives-with-python.ipynb
@@ -285,7 +285,12 @@
                 }
             ],
             "source": [
-                "x = np.linspace(-5, 2, 1000)\n",
+                "x = np.linspace(-4, 2, 1000)\n"
+                "def f(x):\n",
+                "    return -x**5 - 2*x**4 + 19*x**3 + 32*x**2 - 48*x",
+                "def df(x):\n",
+                "    h = 0.000001\n",
+                "    return (f(x + h) - f(x))/h"
                 "plt.plot(x, f(x), label = '$f(x)$')\n",
                 "plt.plot(x, df(x), label = '$f\\'(x)$')\n",
                 "plt.axhline(color = 'black')\n",