First:
[tex](f\circ g)(x)=\sqrt[]{-x-1}+9[/tex]The domain of this function is when the term under the root is positive or 0 because there is no root for a negative number in the real numbers, this only happens when:
[tex]-x-1\ge0\Rightarrow-x\ge1\Rightarrow x\leq-1[/tex]Then, the domain is when x is:
[tex]x=(-\infty,-1\rbrack[/tex]Then, for the second part:
[tex](g\circ f)(x)=\sqrt[]{-(x+9)-1}=\sqrt[]{-x-10}[/tex]The domain for this function is only when the term under the root is positive or 0, so:
[tex]-x-10\ge0\Rightarrow-x\ge10\Rightarrow x\leq-10[/tex]Then, the domain is:
[tex]x=(-\infty,-10\rbrack[/tex]