`B=((x√x+x+√x)/(x√x-1)-(√x+3)/(1-√x)).(x-1)/(2x+√x-1)`
`⇔B=((√x(x+√x+1))/((√x-1)(x+√x+1))+(√x+3)/(√x-1)).((√x-1)(√x+1))/((√x+1)(2√x-1))`
`⇔B=((√x)/(√x-1)+(√x+3)/(√x-1)).(√x-1)/(2√x-1)`
`⇔B=(√x+3)/(√x-1).(√x-1)/(2√x-1)`
`⇔B=(2√x+3)/(2√x-1)`
`B<0`
ta có : `2√x+3>0`
`⇒2√x-1<0`
`⇔2√x<1`
`⇔√x<1/2`
`⇔x<1/4`