Đáp án: :))))))))))))))))))))
Giải thích các bước giải:
VT = ($\frac{\sqrt[]{a} }{1-\sqrt[]{a} }$ + $\frac{\sqrt[]{a} }{1+\sqrt[]{a} }$ ) : $\frac{\sqrt[]{a} }{a-1}$
= $\frac{\sqrt[]{a} (1+\sqrt[]{a})+\sqrt[]{a}(1-\sqrt[]{a}) }{(1-\sqrt[]{a})(1+\sqrt[]{a})}$ : $\frac{\sqrt[]{a}}{a-1}$
= $\frac{\sqrt[]{a}+a+\sqrt[]{a}-a}{1-a}$ : $\frac{\sqrt[]{a}}{a-1}$
= $\frac{2\sqrt[]{a} }{1-a}$ . $\frac{-(1-a)}{\sqrt[]{a} }$
= -2 = VP ( đpcm)
