Consider the function $f(x)=\frac{4x-5}{x+5}$

$($a$)$ The domain of $f$ is xin

$($b$)$ The horizontal asymptotes of $f$ are $y=$

$($c$)$ The vertical asymptotes of $f$ are $x=$

$($d$)$ Find all critical numbers $c$ of $f.,c=$

$($e$)f$ is increasing for xin

$($f$)f$ is decreasing for $x$

$($g$)f$ is concave up for xin

$($h$)f$ is concave down for xin

$($i$)$ The inflection points of $f$ occur at $x=$