Factor the denominator using the difference of squares formula, a² − b² = (a−b)(a+b).

A proper fraction is a rational expression where the degree of the numerator polynomial is less than the degree of the denominator polynomial. An improper fraction is a rational expression where the degree of the numerator polynomial is greater than or equal to the degree of the denominator polynomial.

The union of two sets $A$ and $B$, denoted by $A \cup B$, is the set containing all elements that are members of $A$, or members of $B$, or members of both.
Example: If $A = \{1, 2, 3\}$ and $B = \{3, 4, 5\}$, then $A \cup B = \{1, 2, 3, 4, 5\}$.

The Cartesian product $M \times L$ is the set of all ordered pairs $(m, l)$ where $m \in M$ and $l \in L$.
Given $M = \{c, d\}$ and $L = \{a, b\}$.

The Cartesian product is $\boxed{\{(c, a), (c, b), (d, a), (d, b)\}}$.

A subset is a set containing some or all of the elements of the original set.
Two subsets of $\{a,b\}$ are $\boxed{\emptyset}$ and $\boxed{\{a\}}$. (Other valid subsets include $\{b\}$ and $\{a,b\}$).

$A'$ (the complement of $A$) consists of all elements in the universal set $U$ that are not in $A$.
Given $U = \{1, 2, 3, 4, 5, 6, 7, 8, 9, 10\}$ and $A = \{2, 3, 5, 7\}$.
To find $A'$, we remove the elements of $A$ from $U$.

The complement of $A$ is $\boxed{\{1, 4, 6, 8, 9, 10\}}$.

The median is the middle value in a dataset when the values are arranged in numerical order. If there is an even number of data points, the median is the average of the two middle values. The mode is the value that appears most frequently in a dataset. A dataset can have one mode, multiple modes, or no mode.

The arithmetic mean ($\bar{x}$) is the sum of all values divided by the number of values ($n$).

The range is the difference between the maximum and minimum values in a dataset.