Đáp án:
Điều kiện xác định:\(\begin{cases}a>0\\\sqrt{a}-1\ne0\\\sqrt{a}-2\ne0\\\end{cases}\)
`<=>` \(\begin{cases}a>0\\\sqrt{a}\ne1\\\sqrt{a}\ne2\\\end{cases}\)
`<=>` \(\begin{cases}a>0\\a\ne1\\a\ne4\\\end{cases}\)
`10)B=(1/(sqrta-1)-1/(sqrta)):((sqrta+1)/(sqrta-2)-(sqrta+2)/(sqrta-1))`
`=(sqrta/(sqrta(sqrta-1))-(sqrta-1)/(sqrta(sqrta-1))):(((sqrta-1)(sqrta+1)-(sqrta-2)(sqrta+2))/((sqrta-1)(sqrta-2)))`
`=((sqrta-(sqrta-1))/(sqrta(sqrta-1))):(x-1-(x-4))/((sqrta-1)(sqrta-2)))`
`=1/(sqrta(sqrta-1)):3/((sqrta-1)(sqrta-2))`
`=(sqrta-2)/(3sqrta)`
