Answer
With $g(x)=\sqrt{x}$, and $f(x)=\sqrt{1+x}$,
$H(x)=f[g(x)]=f\circ g(x)$
Work Step by Step
If we were to calculate by hand,
we would find the square root of the number $\qquad$...$ g(x)=\sqrt{x}$,
then find the square root of (the number +1)$\qquad$ .... $f(x)=\sqrt{1+x}$
In this way, $H(x)=f(g(x))=f\circ g(x)$