`ĐKXĐ:x\ge0,x\ne1`
`A={\sqrt{x}+1}/{x-1}-{x+2}/{x\sqrt{x}-1}-{\sqrt{x}+1}/{x+\sqrt{x}+1}`
`={\sqrt{x}+1}/{(\sqrt{x}+1)(\sqrt{x}-1)}-{x+2}/{(\sqrt{x}-1)(x+\sqrt{x}+1)}-{\sqrt{x}+1}/{x+\sqrt{x}+1}`
`={1}/{\sqrt{x}-1}-{x+2}/{(\sqrt{x}-1)(x+\sqrt{x}+1)}-{\sqrt{x}+1}/{x+\sqrt{x}+1}`
`={x+\sqrt{x}+1}/{(\sqrt{x}-1)(x+\sqrt{x}+1)}-{x+2}/{(\sqrt{x}-1)(x+\sqrt{x}+1)}-{(\sqrt{x}+1)(\sqrt{x}-1)}/{(\sqrt{x}-1)(x+\sqrt{x}+1)}`
`={x+\sqrt{x}+1-(x+2)-(\sqrt{x}+1)(\sqrt{x}-1)}/{(\sqrt{x}-1)(x+\sqrt{x}+1)}`
`={x+\sqrt{x}+1-x-2-(x-1)}/{(\sqrt{x}-1)(x+\sqrt{x}+1)}`
`={x+\sqrt{x}+1-x-2-x+1}/{(\sqrt{x}-1)(x+\sqrt{x}+1)}`
`={-x+\sqrt{x}}/{(\sqrt{x}-1)(x+\sqrt{x}+1)}`
`={-\sqrt{x}(\sqrt{x}-1)}/{(\sqrt{x}-1)(x+\sqrt{x}+1)}`
`={-\sqrt{x}}/{x+\sqrt{x}+1}`
Vậy với `x\ge0,x\ne1` thì `A={-\sqrt{x}}/{x+\sqrt{x}+1}`
