Đáp án + Giải thích các bước giải:
`A=(\sqrtx)/(\sqrtx -5)-(10\sqrtx)/(x-25)-5/(\sqrtx +5)(x>=0,x\ne25)`
`= (\sqrtx)/(\sqrtx -5)-(10\sqrtx)/((\sqrtx -5)(\sqrtx +5))-5/(\sqrtx +5)`
`=(\sqrtx(\sqrtx +5))/((\sqrtx -5)(\sqrtx +5))-(10\sqrtx)/((\sqrtx -5)(\sqrtx +5))-(5(\sqrtx -5))/((\sqrtx -5)(\sqrtx +5))`
`=(x+5\sqrtx -10\sqrtx -5\sqrtx +25)/((\sqrtx -5)(\sqrtx +5))`
`=(x -10\sqrtx+25)/((\sqrtx -5)(\sqrtx +5))`
`=((\sqrtx -5)^2)/((\sqrtx -5)(\sqrtx +5))`
`=(\sqrtx -5)/(\sqrtx +5)`
Ta có:`\sqrtx -5<\sqrtx +5`
`⇒(\sqrtx -5)/(\sqrtx +5)<(\sqrtx +5)/(\sqrtx +5)`
`⇒(\sqrtx -5)/(\sqrtx +5)<1`
Mà `1<2`
`⇒(\sqrtx -5)/(\sqrtx +5)<2`
`⇒A<2`