Take a look at the applet: Exponential Functions
Every exponential function has a function rule that can be written as $f\left(x\right)=b\cdot {g}^{x}+d$.
To obtain this form you may need to use the computation rules for powers.
You can obtain the graph of
$f$ by using the following transformations on
$y={g}^{x}$:
multiplication with respect to the $y$ -axis with $b$;
translation along the $y$ -axis with $d$ units.
Therefore the graph determined by
$f$ has a horizontal asymptote: the line
$y=d$.
You find the potential zero by solving
$b\cdot {g}^{x}+d=0$. This often requires a calculator.