Rút gọn biểu thức A=2 sqrta-a sqrtfrac4a+a2 sqrtfrac9a3 vói a >0 ?

Ta có:

$A=2 \sqrt{a}-a \sqrt{\frac{4}{a}}+a^{2} \sqrt{\frac{9}{a^{3}}}=2 \sqrt{a}-\sqrt{\frac{4 a^{2}}{a}}+\sqrt{\frac{9 a^{4}}{a^{3}}}$

$=2 \sqrt{a}-\sqrt{4 a}+\sqrt{9 a}=2 \sqrt{a}-2 \sqrt{a}+3 \sqrt{a}$

$=(2-2+3) \cdot \sqrt{a}=3 \sqrt{a}$