Answer
See below.
Work Step by Step
We know that $\log_a1=0$ and that $\log_a x+\log_a y=log_a (x\cdot y)$, hence $\log_a{(\sqrt x+\sqrt{x-1})}+\log_a{(\sqrt x-\sqrt{x-1})}=\log_a{(\sqrt x+\sqrt{x-1})(\sqrt x-\sqrt{x-1})}=\log_a{(x-(x-1))}=\log_a{1}=0$
