for a set of coordinate pairs, a function set, will not have a repeat on the x-coordinate, namely, the "x"s do not repeat, no x-repeats.
now, look at 4) [tex]\bf \begin{array}{ccll}
x&y\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
-2&-4\\
0&-2\\
2&0\\
4&2
\end{array}[/tex]
the x-values are -2, 0, 2, 4, no repeats, so it IS a function.
10)
[tex]\bf \{(-1,3),(\stackrel{\stackrel{re peat}{\downarrow }}{1},4),(4,7),(\stackrel{\stackrel{re peat}{\downarrow }}{1},0)\}\impliedby \textit{not a function}[/tex]
the other ones, you can check for that, you're correct. For example for 6), the graph doesn't pass the "vertical line test", so is not a function.
