Fix typo in Problem 1a, fixes #10

src/4_vector_spaces_QM.md

@@ -243,7 +243,7 @@ $$
 $$
 Let $a=6+5i$ and answer the following questions:
 
-*(a)*. Calculate $a|A\rangle$, $a |B\rangle$, and $a( |A\rangle+|B\rangle)$. Show that $a(|A\rangle+|B\rangle)=a|A\rangle+|B\rangle)$.
+*(a)*. Calculate $a|A\rangle$, $a |B\rangle$, and $a( |A\rangle+|B\rangle)$. Show that $a(|A\rangle+|B\rangle)=a|A\rangle+a|B\rangle$.
 
 *(b)*. Find the inner products $\langle A | B\rangle$ and $\langle B | A\rangle $. What is the relationship between them?