Giải thích các bước giải:
1) `T=-sqrt5+sqrt((1-sqrt5)^2)`
`=-sqrt5+|1-sqrt5|`
`=-sqrt5+sqrt5-1`
`=-1`
2) a) `P=(sqrtx/(sqrtx+1)-sqrtx/(sqrtx-1)):2/(sqrtx+1)` `(x>0)`
`=((x-sqrtx)/(x-1)-(x+sqrtx)/(x-1)):2/(sqrtx+1)`
`=((x-sqrtx-x-sqrtx)/(x-1)).(sqrtx+1)/2`
`=(-2sqrtx)/(x-1).(x-1)/(2sqrtx-2)`
`=(-2sqrtx)/(2sqrtx-2)=-(sqrtx)/(sqrtx-1)`
b) `P=-2`
`<=>-(sqrtx)/(sqrtx-1)=-2`
`<=>sqrtx=2(sqrtx-1)`
`<=>2sqrtx-2=sqrtx`
`<=>2sqrtx-sqrtx=2`
`<=>sqrtx=2`
`<=>x=4` `(t//m)`
