Rút gọn biểu thức (A = frac{{sqrt x }}{{sqrt x + 1}} + frac{3}{{sqrt x }} – frac{{5sqrt x + 3}}{{x + sqrt x }},,,,,left( {x > 0} right).)

(begin{array}{l}A = frac{{sqrt x }}{{sqrt x  + 1}} + frac{3}{{sqrt x }} – frac{{5sqrt x  + 3}}{{x + sqrt x }} = frac{{sqrt x .sqrt x  + 3.left( {sqrt x  + 1} right) – left( {5sqrt x  + 3} right)}}{{sqrt x .left( {sqrt x  + 1} right)}}\,,, = frac{{x + 3sqrt x  + 3 – 5sqrt x  – 3}}{{sqrt x .left( {sqrt x  + 1} right)}} = frac{{x – 2sqrt x }}{{sqrt x .left( {sqrt x  + 1} right)}}\,, = frac{{sqrt x left( {sqrt x  – 2} right)}}{{sqrt x .left( {sqrt x  + 1} right)}} = frac{{sqrt x  – 2}}{{sqrt x  + 1}}.end{array})

Chọn D.