A Complete Set of Examples and Detailed Practice Solutions
Understanding the domain (all possible $x$-values) and range (all possible $y$-values) of a relation from its graph is a critical algebraic skill. This page provides 10 comprehensive examples covering finite segments, infinite rays, and closed curves.
Identify the domain, range, and determine if the relation is a function:
Domain: $x$ ranges from point $A(-2, -4)$ to $B(4, -6)$:
\[ -2 \le x \le 4 \]Range: The lowest point is $B(4, -6)$ and highest is $C(2, 2)$:
\[ -6 \le y \le 2 \]Is it a function? Yes. No vertical line crosses the graph more than once.
Domain: Smallest $x$ at $A(-3, -5)$, largest at $B(8, 4)$:
\[ -3 \le x \le 8 \]Range: Smallest $y$ at $A(-5)$, largest at $B(4)$:
\[ -5 \le y \le 4 \]Is it a function? Yes, it passes the vertical line test.
Domain: From $A(-3, -2)$ to $B(1, -2)$:
\[ -3 \le x \le 1 \]Range: Lowest point $C(-1, -5)$ to highest point $D(-1, 1)$:
\[ -5 \le y \le 1 \]Is it a function? No. A vertical line crosses the graph at multiple points.
Domain: Leftmost point is $A(-3, 0)$. The arrow points infinitely to the right:
\[ x \ge -3 \]Range: Lowest points are $B, C$ at $y = -2$. The arrow points up:
\[ y \ge -2 \]Is it a function? Yes.
Domain: Leftmost is $A(-2, -3)$ with an open circle. Graph extends right:
\[ x > -2 \]Range: Lowest is $y = -3$ (excluded). Graph extends up:
\[ y > -3 \]Is it a function? Yes.
Domain: From $A(-8, -0.5)$ to $B(4, 0)$:
\[ -8 \le x \le 4 \]Range: Lowest point $C(-3, -5)$ to highest $B(4, 0)$:
\[ -5 \le y \le 0 \]Function: Yes.
Domain: $A(-2, 4)$ to $B(4, 6)$:
\[ -2 \le x \le 4 \]Range: Lowest $C(2, -2)$ to highest $B(4, 6)$:
\[ -2 \le y \le 6 \]Function: Yes.
Domain: Extends infinitely left, ends at $A(4, 2)$:
\[ x \le 4 \]Range: Lowest $y = -2$ (points B and C), extends infinitely up:
\[ y \ge -2 \]Function: Yes.
Domain: From $A(-5, -1)$ to $B(1, -1)$:
\[ -5 \le x \le 1 \]Range: Lowest $C(-2, -3)$ to highest $D(-2, 1)$:
\[ -3 \le y \le 1 \]Function: No. This is a closed curve; vertical lines hit it twice.
Domain: Starts at $A(-3, 1.8)$ with an open circle, extends infinitely right:
\[ x > -3 \]Range: Highest is $B(-2, 2)$, extends infinitely down:
\[ y \le 2 \]Function: Yes.