Question

\(\dfrac{\sqrt{28y^6}}{\sqrt{7y^4}}vớiy< 0\)

Answer 1

\(ĐKXĐ:y\ne0\)

\(\dfrac{\sqrt{28y^6}}{\sqrt{7y^4}}=\sqrt{\dfrac{28y^6}{7y^4}}=\sqrt{4y^2}=\left|2y\right|=-2y\)

Answer 2

`\sqrt{28y^6}/\sqrt{7y^4}`

`=\sqrt{(2y^3)^2 .7}/\sqrt{7.(y^2)^2}`

`=[|2y^3|.\sqrt{7}]/[\sqrt{7}.|y^2|]`

`=[-2y^3]/[y^2]`   `(y < 0)`

`=-2y`

Answer 3

`Đk : y≠0`

\(\dfrac{\sqrt{28y^6}}{\sqrt{7y^4}}=\sqrt{\dfrac{28y^6}{7y^4}}\)

\(=\sqrt{\dfrac{4.7y^4.y^2}{7y^4}}=\sqrt{4y^2}\)

\(=\sqrt{\left(2y\right)^2}=\left|2y\right|=-2y\left(với:y< 0\right)\)