diff --git a/book_equations.ipynb b/book_equations.ipynb
index f2ffaee..5f92380 100644
--- a/book_equations.ipynb
+++ b/book_equations.ipynb
@@ -818,11 +818,11 @@
     "**Equation 13-1: Computing the output of a neuron in a convolutional layer**\n",
     "\n",
     "$\n",
-    "z_{i,j,k} = b_k + \\sum\\limits_{u = 1}^{f_h} \\, \\, \\sum\\limits_{v = 1}^{f_w} \\, \\, \\sum\\limits_{k' = 1}^{f_{n'}} \\, \\, x_{i', j', k'} . w_{u,v,k', k}\n",
+    "z_{i,j,k} = b_k + \\sum\\limits_{u = 0}^{f_h - 1} \\, \\, \\sum\\limits_{v = 0}^{f_w - 1} \\, \\, \\sum\\limits_{k' = 0}^{f_{n'} - 1} \\, \\, x_{i', j', k'} . w_{u, v, k', k}\n",
     "\\quad \\text{with }\n",
     "\\begin{cases}\n",
-    "i' = u.s_h+f_h-1 \\\\\n",
-    "j' = v.s_w+f_w-1\n",
+    "i' = i \\times s_h + u \\\\\n",
+    "j' = j \\times s_w + v\n",
     "\\end{cases}\n",
     "$\n",
     "\n",