one element Table (i) defines $y$ as a function of $x$, but not table (ii).
Work Step by Step
A function $f$ is a rule that assigns to each element $x$ in a set $A$ exactly ___one___ element called $f(x)$ in a set $B$. Table (i) defines $y$ as a function of $x$ because there are unique $y$ values for each $x$. However, table (ii) does not define a function, because $f(1)$ has two values (5 and 7).