## College Algebra (10th Edition)

$x=-4$
Note that $81=3^4$. Thus, the given equation is equivalent to: $3^{-x} = 3^4$ Use the rule $a^m=a^n \longrightarrow m = n$ to obtain: $-x = 4$ Multiply $-1$ to both sides of the equation to obtain: $x=-4$