Cho biểu thức A= ( x căn bậc hai x-1 / 1+ x + căn bậc hai x) ( căn bậc hai x+ 1/ x-1- căn bậc hai x-2 / x - căn bậc hai x -2)
\(A = \frac{{{{\left( {\sqrt x } \right)}^3} - 1}}{{1 + \sqrt x + x}}.\left[ {\frac{{\sqrt x + 1}}{{\left( {\sqrt x + 1} \right)\left( {\sqrt x - 1} \right)}} - \frac{{\sqrt x - 2}}{{\left( {\sqrt x + 1} \right)\left( {\sqrt x - 2} \right)}}} \right]\) |
\( = \frac{{(\sqrt x - 1)(x + \sqrt x + 1)}}{{1 + \sqrt x + x}}.\left[ {\frac{{\sqrt x + 1}}{{\left( {\sqrt x + 1} \right)\left( {\sqrt x - 1} \right)}} - \frac{{\sqrt x - 2}}{{\left( {\sqrt x + 1} \right)\left( {\sqrt x - 2} \right)}}} \right]\) |
\( = \left( {\sqrt x - 1} \right)\left( {\frac{1}{{\sqrt x - 1}} - \frac{1}{{\sqrt x + 1}}} \right)\) |
\( = \left( {\sqrt x - 1} \right)\frac{2}{{\left( {\sqrt x - 1} \right)\left( {\sqrt x + 1} \right)}}\) |
\( = \frac{2}{{\sqrt x + 1}}.\) |