Bài `1:`
`a)\sqrt{27x^2}(x>=0)`
`=3x\sqrt{3}`
`b)\sqrt{8xy^2}(x>=0,y<=0)`
`=-2y\sqrt{2x}`
`c)\sqrt{25x^2}(x>=0)`
`=5x`
`d)\sqrt{48xy^4}(x>=0,y∈R)`
`=4y^2\sqrt{3x}`
Bài `2:`
`a)a\sqrt{13}(a>=0)`
`=\sqrt{13a^2}`
$b)a\sqrt{\dfrac{-15}{a}}(a<0)$
$=\sqrt{\dfrac{15a^2}{a}}$
$=\sqrt{15a}$
$c)\dfrac{a}{2}\sqrt{\dfrac{12}{a}}(a>0)$
$=\sqrt{\dfrac{12a^2}{4a}}$
$=\sqrt{3a}$
`d)a\sqrt{2}(a<=0)`
`=\sqrt{2a^2}`
