Đáp án:
`a. 5xy sqrt{\frac{25x^2}{y^6}}`
`= 5xy xx \frac{sqrt{25x^2}}{sqrt{y^6}}`
`= 5xy xx \frac{sqrt25 sqrt{x^2}}{sqrt{(y^3)^2}}`
`= 5xy xx \frac{5|x|}{|y^3|}`
`= 5xy xx \frac{5(-x)}{y^3}` (`x<0, y>0`)
`= -\frac{25x^2}{y^2}`
`b. 0,2x^3y^3sqrt{\frac{16}{x^4y^8}}`
`= 1/5x^3y^3 xx \frac{sqrt16}{sqrt{x^4y^8}}`
`= 1/5x^3y^3 xx \frac{4}{|x^2||y^4|}`
`= 1/5x^3y^3 xx \frac{4}{x^2y^4}`(`x^2\ge0, y^4=(y^2)^2\ge0`)
`= 1/5x xx 4/y`
`= \frac{4x}{5y}`
