Answer
false
Work Step by Step
RECALL:
(1) $\dfrac{1}{a^x} = a^{-x}$
(2) $(a^m)^n=a^{mn}$
Use rule (1) above to obtain:
$\left(\dfrac{1}{3}\right)^x = \left(3^{-1}\right)^x$
Use rule (2) above to obtain:
$\left(3^{-1}\right)^x = 3^{-1(x)} = 3^{-x}$
Note that $3^x \ne 3^{-x}$, so $y=3^x$ is not equivalent to $y=\left(\dfrac{1}{3}\right)^x$.
This means that they have different graphs.
Thus, the given statement is false.