Relation Function
1. Determine the domain, range, and whether the relation is a function for each given relation.
1.a) Relation: ${\{(-3,0), (-1,1), (0,1), (4,5), (0,6)\}}$
- Domain: all x-values ${\{-3, -1, 0, 4\}}$
- Range: all y-values ${\{0, 1, 5, 6\}}$
- Is it a function? No, because the input $0$ maps to two different outputs ($1$ and $6$).
1.b) Relation: $y = 4 - x$
- Domain: All real numbers (since $x$ can be anything)
- Range: All real numbers (linear function)
- Is it a function? Yes, each $x$ has exactly one $y$.
1.c) Relation from table:
\begin{tabular}{c|ccccc}
x & -4 & -2 & 0 & 2 & 4 \\ \hline
y & 4 & 2 & 0 & -2 & -4
\end{tabular}
- Domain: ${\{-4, -2, 0, 2, 4\}}$
- Range: ${\{4, 2, 0, -2, -4\}}$
- Is it a function? Yes, each input has one output.
1.d) Relation: $x^2 + y^2 = 16$
- Domain: ${x \in [-4,4]}$ (since $|x| \le 4$ for real $y$)
- Range: ${y \in [-4,4]}$
- Is it a function? No, because for some $x$ there are two $y$ values (circle).
2. Rule to determine function from graph: A relation is a function if any vertical line intersects the graph at most once (Vertical Line Test).
2.a) Relation: ${(-2,1), (1,1), (0,0), (1,-1), (1,-2), (2,-2)}$
- x=1 maps to three different y values, so not a function.
2.b) $y = 4 - 3x$
- Linear function, passes vertical line test, so it's a function.
2.c) $y = (x - 2)^2 + 4$
- Parabola opening upward, passes vertical line test, so it is a function.
2.d) $x^2 + y^2 = 1$
- Circle with radius 1, fails vertical line test, not a function.
2.e) $y = \frac{1}{x}$
- Hyperbola, passes vertical line test except at $x=0$ (not in domain), so it's a function.
2.f) $y = \sqrt{x}$
- Passes vertical line test, domain $x\ge0$, so it's a function.
Summary:
- Functions: 1.b, 1.c, 2.b, 2.c, 2.e, 2.f
- Not functions: 1.a, 1.d, 2.a, 2.d