\(\dfrac{\sqrt{0,4}}{\sqrt{2,5}}\)= ?
\(\dfrac{2}{5}\). \(\dfrac{4}{25}\). \(\dfrac{1}{5}\). \(-\dfrac{2}{5}\). Hướng dẫn giải:\(\dfrac{\sqrt{0,4}}{\sqrt{2,5}}=\sqrt{\dfrac{0,4}{2,5}}=\sqrt{\dfrac{4}{25}}=\sqrt{\left(\dfrac{2}{5}\right)^2}=\dfrac{2}{5}\)
