Find the following. f$($x$)=\backslash$sqrt$($x$^(2)-9),$g$($x$)=($x$^(2))/($x$^(2)+1)($a$)($f$+$g$)($x$)=($b$)($f$-$g$)($x$)=($c$)($fg$)($x$)=($d$)(($f$)/($g$))($x$)=$ What is the domain of $($f$)/($g$)?($Enter your answer using interval notation.$)$