b) ĐKXĐ: ..............................$=\frac{1}{\sqrt{a}.(\sqrt{a}-1)}.\frac{(\sqrt{a}-1)(\sqrt{a}-2)}{a-1-(a-4)}=\frac{\sqrt{a}-2}{3\sqrt{a}}$
b) ĐKXĐ: ..............................$=\frac{1}{\sqrt{a}.(\sqrt{a}-1)}.\frac{(\sqrt{a}-1)(\sqrt{a}-2)}{a-1-(a-4)}=\frac{\sqrt{a}-3}{\sqrt{a}}$
b) ĐKXĐ: ..............................$=\frac{1}{\sqrt{a}.(\sqrt{a}-1)}.\frac{(\sqrt{a}-1)(\sqrt{a}-2)}{a-1-(a-4)}=\frac{\sqrt{a}-
2}{
3\sqrt{a}}$