Implement problem 5 and a bit more

latex/problems/problem1.tex

@@ -40,5 +40,5 @@ Using the values that we found for $c_1$ and $c_2$, we get
 
 \begin{align*}
     u(x) &= -e^{-10x} + (e^{-10} - 1) x + 1 \\
-         &= 1 - (1 - e^{-10}) - e^{-10x}
+         &= 1 - (1 - e^{-10})x - e^{-10x}
 \end{align*}