1) ĐKXĐ :` x≥0`
` x\ne0`
` \sqrt{x}+1\ne0`
` \sqrt{x}-1\ne0`
` ⇔x>0`
` x\ne1`
2)
`A=( \sqrt{x}-1/( \sqrt{x}))((\sqrt{x})/(\sqrt{x}+1)+(\sqrt{x})/(\sqrt{x}-1))`
`⇔((x-1)/\sqrt{x})(\sqrt{x} . (\sqrt{x}-1)+\sqrt{x} . (\sqrt{x}+1))/(x-1)`
`⇔[(x-\sqrt{x}+x+\sqrt{x})/(\sqrt{x})]`
`⇔(2x)/(\sqrt{x})`
`⇔2\sqrt{x}`
