Answer
$f(4)=-162$
Work Step by Step
The given function is
$\Rightarrow f(x)=-2(3)^x$
Substitute $4$ for $x$.
$\Rightarrow f(4)=-2(3)^4$
$\Rightarrow f(4)=-2\cdot 3^4$
Use $3^4=81$.
$\Rightarrow f(4)=-2\cdot 81$
Simplify.
$\Rightarrow f(4)=-162$
