Rút gọn biểu thức \(\dfrac{...

D

- Hướng dẫn giải

 $\dfrac{{a + b}}{{{b^2}}}.\sqrt {\dfrac{{{a^2}{b^4}}}{{{a^2} + 2ab + {b^2}}}}$

$= \dfrac{{a + b}}{{{b^2}}}\sqrt {\dfrac{{{{\left( {a{b^2}} \right)}^2}}}{{{{\left( {a + b} \right)}^2}}}}$

$= \dfrac{{a + b}}{{{b^2}}} \cdot \dfrac{{\left| {a{b^2}} \right|}}{{ {a + b} }}$

$= \dfrac{{\left| a \right|.{b^2}}}{{{b^2}}} = \left| a \right|$