`P=\frac{\sqrt{x}+3}{\sqrt{x}+1}(x>=0)`
`=1+\frac{2}{\sqrt{x}+1}`
Vì `\sqrt{x}+1>=1`
`->\frac{2}{\sqrt{x}+1}<=2`
`->1+\frac{2}{\sqrt{x}+1}>1`
`->P>1`
`b)\frac{\sqrt{x}+3}{\sqrt{x}+1}`
Ta có: `\sqrt{x}+3>=3`
`\sqrt{x}+1>=1`
`->\frac{\sqrt{x}+3}{\sqrt{x}+1}>0`
`->P=|P|`