Edits

Advanced/Size of Sets/parts/3 functions.tex

@@ -205,12 +205,6 @@ Is this function one-to-one? Is it onto?
 
 \vfill
 
-\problem{}
-Consider the function $f: \mathbb{N} \to \mathbb{N}$ defined by $f(x) = x^2$. \par
-Is this function one-to-one? Is it onto?
-
-\vfill
-
 \problem{}
 Consider the function $f: \mathbb{Z} \to \mathbb{Z}$ defined below. \par
 Is this function one-to-one? Is it onto?
@@ -375,4 +369,7 @@ Show that no bijection between $A$ and $B$ exists.
 
 Intuitively, you can think of a bijection as a \say{matching} between elements of $A$ and $B$. If we were to draw a bijection, we'd see an arrow connecting every element in $A$ to every element in $B$. If a bijection exists, every element of $A$ directly corresponds to an element of $B$, therefore $A$ and $B$ must have the same number of elements.
 
+\definition{}
+We say two sets $A$ and $B$ are \textit{equinumerous} if there exists a bijection $f: A \to B$.
+
 \pagebreak