Fix: Missing constant

Author: B67687

discrete-mathematics/series-and-sequences/triangular-numbers-and-their-sum.ipynb

@@ -124,7 +124,7 @@
     "Thus, when we substitute it back in\n",
     "\n",
     "$$\n",
-    "\\sum_{k=1}^n k(k+1) = \\dfrac{1}{2} \\cdot \\boxed{\\dfrac{n(n+1)(n+2)}{3}}\n",
+    "\\dfrac{1}{2} \\sum_{k=1}^n k(k+1) = \\dfrac{1}{2} \\cdot \\boxed{\\dfrac{n(n+1)(n+2)}{3}}\n",
     "$$\n",
     "\n",
     "---\n",
@@ -133,7 +133,7 @@
     "\n",
     "$$\n",
     "\\boxed{\n",
-    "    \\sum_{k=1}^n k(k+1) = \\dfrac{n(n+1)(n+2)}{6}\n",
+    "    \\sum_{k=1}^n \\dfrac{k(k+1)}{2} = \\dfrac{n(n+1)(n+2)}{6}\n",
     "}\n",
     "$$\n"
    ]
@@ -155,7 +155,14 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.12.9"
+   "version": "3.13.9"
+  },
+  "widgets": {
+   "application/vnd.jupyter.widget-state+json": {
+    "state": {},
+    "version_major": 2,
+    "version_minor": 0
+   }
   }
  },
  "nbformat": 4,