diff --git a/psets/pset5.ipynb b/psets/pset5.ipynb
index 29d3154..2fbfde7 100644
--- a/psets/pset5.ipynb
+++ b/psets/pset5.ipynb
@@ -44,7 +44,7 @@
     "$$\n",
     "for some $r > 0$, $m \\times n$ matrix $A$ (of rank $n$), and $b \\in \\mathbb{R}^m$ — that is, least-squares optimization with the solution constrained to lie inside a sphere of radius $r$.\n",
     "\n",
-    "**(a)** What is the Lagrange dual function $g(\\lambda)$?   (You can give a closed-form expression.  Hint: review Tikhonov-regularized least-squares.)   Define a corresponding Julia function `g(λ; r=1.0)` for the sample parameters given below (this syntax defines an optional keyword argument `r` that defaults to $r=1$).  Make a plot of $$g(\\lambda)$$ for $$r=1$$ and $$r=0.5$$ to verify that it looks concave with a single maximum.\n",
+    "**(a)** What is the Lagrange dual function $g(\\lambda)$?   (You can give a closed-form expression.  Hint: review Tikhonov-regularized least-squares.)   Define a corresponding Julia function `g(λ; r=1.0)` for the sample parameters given below (this syntax defines an optional keyword argument `r` that defaults to $r=1$).  Make a plot of $g(\\lambda)$ for $r=1$ and $r=0.5$ to verify that it looks concave with a single maximum.\n",
     "\n",
     "**(b)** If the unconstrained least-square solution $\\hat{x} = (A^T A)^{-1} A^T b$ satisfies $\\Vert \\hat{x} \\Vert_2 < r$, then what must be true of the derivative $g'(0)$?  What if $\\Vert \\hat{x} \\Vert_2 > r$?\n",
     "\n",