Answer
$y=\sqrt{x-1}-3$.
Work Step by Step
Graph of square root function $\sqrt{x}$ is moved $1$ unit right and $3$ units down to get the given graph.
Translation $1$ unit right $~\rightarrow~$ $\sqrt{x-1}$
Translation $3$ units down $~\rightarrow~$ $\sqrt{x-1}-3$
So, the new equation is $y=\sqrt{x-1}-3$.
