`#huy`
`A-N=(\sqrt{x}-1)/(\sqrt{x}+1)-(\sqrt{x}-3)/(2\sqrt{x})`
`=(2x-2\sqrt{x}-(\sqrt{x}+1)(\sqrt{x}-3))/(2\sqrt{x}(\sqrt{x}+1))`
`=(2x-2\sqrt{x}-x2\sqrt{x}+3)/(2x+2\sqrt{x})`
`=(x+3)/(2\sqrt{x}(\sqrt{x}+1))`
Mà `x>=0=>(x+3)/(2\sqrt{x}(\sqrt{x}+1))>0`
`=>A>N`