Okay, here we have this:
We need to meke the composition (f•g)(x), so in the function f we will replace x with the function g:
[tex]\begin{gathered} \mleft(f•g\mright)\mleft(x\mright)=\sqrt[]{2(x-1)+10} \\ =\sqrt[]{2x-2+10} \\ =\sqrt[]{2x+8} \end{gathered}[/tex]Now let's find the domain of (f•g)(x):
2X+8≥0
2X≥-8
X≥-4
Finally we obtain the following domain: [-4,∞)