Bài làm :
p,
`2/(2a-1)\sqrt{5a^2.(1-4a+4a^2)}`
`=2/(2a-1)\sqrt{5a^2.(4a^2-4a+1)}`
`=2/(2a-1)\sqrt{5a^2.(2a-1)^2}`
`=2/(2a-1) . \sqrt{5} . |a| . |2a-1|`
`=2/(2a-1) . \sqrt{5} . a. (2a-1)` ( vì `a > 0,5 <=>2a>1<=>2a-1>0` )
`=(2.\sqrt{5} . a.(2a-1))/(2a-1)`
`=2\sqrt{5} a`
$\\$
q, `2\sqrt{3x}-4\sqrt{3x}+27-3\sqrt{3x}`
`=(2-4-3)\sqrt{3x} + 27`
`=-5\sqrt{3x}+27`
