`#tnvt`
`a)\sqrt{9x+27}-1/4\sqrt{16x+48}+\sqrt{x+3}=6(x>=-3)`
`<=>3\sqrt{x+3}-1/4 .4\sqrt{x+3}+\sqrt{x+3]=6`
`<=>3\sqrt{x+3}-\sqrt{x+3}+\sqrt{x+3}=6`
`<=>3\sqrt{x+3}=6`
`<=>\sqrt{x+3]=2`
`<=>x+3=4`
`<=>x=1(tm)`
Vậy `S={1}`
`b)2+\sqrt{2x-1}=x(x>=1/2)`
`<=>\sqrt{2x-1}=x-2(x>=2)`
`<=>2x-1=(x-2)^2`
`<=>x^2-4x+4-2x+1=0`
`<=>x^2-6x+5=0`
`<=>x^2-x-5x+5=0`
`<=>x(x-1)-5(x-1)=0`
`<=>(x-5)(x-1)=0`
`<=>[(x=5(tm)),(x=1(ktm)):}`
Vậy `S={5}`
