Rút gọn biểu thức P. A.\(P = \frac{{\sqrt x - 1}}{{\sqrt x }}\) B.\(P = \frac{{\sqrt x + 1}}{{\sqrt x - 1}}\) C.\(P = \frac{{\sqrt x + 1}}{{\sqrt x }}\) D.\(P = \frac{{\sqrt x - 1}}{{\sqrt x + 1}}\)
Đáp án đúng: C Giải chi tiết:\(\begin{array}{l}P = \left( {1 - \frac{1}{{\sqrt x }}} \right):\left( {\frac{{\sqrt x - 1}}{{\sqrt x }} + \frac{{1 - \sqrt x }}{{x + \sqrt x }}} \right) = \frac{{\sqrt x - 1}}{{\sqrt x }}:\left[ {\frac{{\sqrt x - 1}}{{\sqrt x }} + \frac{{1 - \sqrt x }}{{\sqrt x \left( {\sqrt x + 1} \right)}}} \right]\\\,\,\,\,\, = \frac{{\sqrt x - 1}}{{\sqrt x }}:\left[ {\frac{{\sqrt x - 1}}{{\sqrt x }}.\left( {1 - \frac{1}{{\sqrt x + 1}}} \right)} \right] = \frac{{\sqrt x - 1}}{{\sqrt x }}:\left[ {\frac{{\sqrt x - 1}}{{\sqrt x }}.\frac{{\sqrt x }}{{\sqrt x + 1}}} \right]\\\,\,\,\,\, = \frac{{\sqrt x - 1}}{{\sqrt x }}:\frac{{\sqrt x - 1}}{{\sqrt x + 1}} = \frac{{\sqrt x - 1}}{{\sqrt x }}.\frac{{\sqrt x + 1}}{{\sqrt x - 1}}\, = \frac{{\sqrt x + 1}}{{\sqrt x }}\,\,\,\left( {x > 0;\,\,x \ne 1} \right)\end{array}\) Chọn C.