Answer
They differ by a constant,
( $G(x)-F(x)=$ Constant.)
Work Step by Step
If $F(x)$ is an antiderivative of $f(x)$, that is $ F'(x)=f(x)$, then the indefinite integral of $f$ is
$\displaystyle \int f(x)dx=F(x)+C.$
This is not one function -- it is a collection of functions, separated by some constant.
These functions have the form
$\quad G(x)=F(x)+C.$
In other words
$G(x)-F(x)=C$,
They differ by a constant,
($G(x)-F(x)=$ Constant).
