`1)` `P=(2x+2)/sqrtx+(xsqrtx-1)/(x-sqrtx)-(xsqrtx+1)/(x+sqrtx)`
`=(2x+2)/sqrtx+((sqrtx-1)(x+sqrtx+1))/(sqrtx(sqrtx-1))-((sqrtx+1)(x-sqrtx+1))/(sqrtx(sqrtx+1))`
`=(2x+2)/sqrtx+(x+sqrtx+1)/(sqrtx)-(x-sqrtx+1)/(sqrtx)`
`=(2x+2+2sqrtx)/(sqrtx)`
`2)` Giả sử `P>5`
`P>5`
`<=>` `2x+2+2sqrtx>5sqrtx`
`<=>` `2x+2-3sqrtx>0`
`<=>` `2(x-3/2sqrtx+9/16)+7/8>0`
`<=>` `2(sqrtx-3/4)^2+7/8>0AAx`
`=>` Giả sử đúng.
Vậy `P>5`
