Answer
True.
Work Step by Step
A function is a correspondence between a first set, called the domain, and a second set, called the range, such that each member of the domain corresponds to exactly one member of the range.
The notation $f(x)$ is read "f of $x,$ " or
"the value of $f$ at $x$ ."
If $x$ is an input, then $f(x)$ is the corresponding output.
So, $f(3)$ is the corresponding output when the input is $x=3.$
(not $f\cdot 3$)
