`G=\sqrt{125a^2}(a<0)`
`=|5a|\sqrt{5}`
`=-5a\sqrt{5}`(vì `a<0)`
`H=1/3\sqrt{225a^2}`
`=1/3.|15a|`
`=5a`(với `a>0)` hoặc `=-5a`(với `a<0)`
$G=\dfrac{2xy^2}{3ab}. \sqrt{\dfrac{9a^3b^4}{8xy^3}}$`(a,b,c,y>0)`
$=\dfrac{2xy^2}{3ab}.|\dfrac{3ab^2}{2y}|.\sqrt{\dfrac{a}{2x}}$
$=\dfrac{2xy^2.3ab^2}{3ab.2y}.\sqrt{\dfrac{a}{2x}}$
$=xyb.\sqrt{\dfrac{a}{2x}}$