#### Answer

$0$;
$0$;
zeros

#### Work Step by Step

RECALL:
(i) The x-intercepts of a function are the x-values for which the value of the function is zero.
(ii) The x-intercepts of a function are also called the function's zeros.
Since $-1$ and $3$ are x-intercepts of the function $f$, then $f(-1)=0$ and $f(3) = 0$.
Therefore. the missing expressions in the given statements are:
$0$;
$0$;
zeros