Answer
(a) $-1$.
(b) $ \{x|x\gt-1\}$.
(a) $25$.
Work Step by Step
Given $f(x)=log_3(x+2)$, we have:
(a) $f(x)=0 \Longrightarrow log_3(x+2)=0 \Longrightarrow x+2=1, x=-1$.
(b) $f(x)\gt0 \Longrightarrow x+2\gt1 \Longrightarrow \{x|x\gt-1\}$.
(a) $f(x)=3 \Longrightarrow log_3(x+2)=3 \Longrightarrow x+2=3^3, x=25$.
