Modified the markdown syntax in Hyperplanes to fix the KaTeX ParseError.

AA2324/course/03_math_recap_eig_pca_3dmm/03_math_recap_eig_pca_3dmm.ipynb

@@ -481,7 +481,8 @@
     "**Hyperplane**: a generalization to higher dimensions of a line ($D=2$) or of a plane ($D=3$).\n",
     "In an $d$-dimensional vector space, a hyperplane has $d-1$ dimensions and **divides the space into two half-spaces.**\n",
     "\n",
-    "$$ \\mathbf{w}\\mathbf{x} + \\mathbf{b} = 0$$ where $\\mathbf{w}$ is a vector normal to the hyperplane and $\\mathbf{b}$ is an offset\n",
+    "$$ \\mathbf{w}\\mathbf{x} + \\mathbf{b} = 0 $$\n",
+    "where $\\mathbf{w}$ is a vector normal to the hyperplane and $\\mathbf{b}$ is an offset\n",
     "\n",
     "<img width='30%' src='https://d2l.ai/_images/space-division.svg' />"
    ]
@@ -499,7 +500,8 @@
     "**Hyperplane**: a generalization to higher dimensions of a line ($D=2$) or of a plane ($D=3$).\n",
     "In an $d$-dimensional vector space, a hyperplane has $d-1$ dimensions and **divides the space into two half-spaces.**\n",
     "\n",
-    "$$ \\mathbf{w}\\mathbf{x} + \\mathbf{b} = 0$$ where $\\mathbf{w}$ is a vector normal to the hyperplane and $\\mathbf{b}$ is an offset\n",
+    "$$ \\mathbf{w}\\mathbf{x} + \\mathbf{b} = 0$$\n",
+    "where $\\mathbf{w}$ is a vector normal to the hyperplane and $\\mathbf{b}$ is an offset\n",
     "\n",
     "<img width='30%' src='https://d2l.ai/_images/space-division-3d.svg' />"
    ]