Đáp án:
`Q=(2sqrtx+3)/(sqrtx-4)(x>=0,x ne 16)`
`1)Q>0`
`<=>(2sqrtx+3)/(sqrtx-4)>0`
Mà `2sqrtx+3>=3>0`
`<=>sqrtx-4>0`
`<=>sqrtx>4`
`<=>x>16`
`2)Q<0`
`<=>(2sqrtx+3)/(sqrtx-4)<0`
Mà `2sqrtx+3>=3>0`
`<=>sqrtx<0`
`<=>sqrtx<4`
`<=>x<16`
`3)Q=2`
`<=>(2sqrtx+3)/(sqrtx-4)>2`
`<=>(2sqrtx+3-2sqrt+8)/(sqrtx-4)>0`
`<=>11/(sqrtx-4)>0`
`<=>sqrtx-4>0`
`<=>sqrtx>4`
`<=>x>16`
`4)Q<-3`
`<=>Q+3<0`
`<=>(2sqrtx+3+3sqrtx-12)/(sqrtx-4)<0`
`<=>(5sqrtx-9)/(sqrtx-4)<0`
`<=>(sqrtx-1,8)/(sqrtx-4)<0`
`<=>` \(\begin{cases}\sqrt{x}-1,8>0\\\sqrt{x}-4<0\\\end{cases}\)
`<=>` \(\begin{cases}x>3,24\\x<16\\\end{cases}\)
`<=>3,24<x<16`
