`#tnvt`
`\frac{4x-12\sqrt{x}+9}{16\sqrt{x}+8}(x>=0)`
`=\frac{(2\sqrt{x})^2-2.2\sqrt{x}.3+3^2}{8(2\sqrt{x}+1)}`
`=\frac{(2\sqrt{x}-3)^2}{8(2\sqrt{x}+1)}`
`∀x` ta có: `{((2\sqrt{x}-3)^2>=0),(2\sqrt{x}+1>=1>0):}`
`=>\frac{(2\sqrt{x}-3)^2}[8(2\sqrt{x}+1)}>=0`
Dấu `=` xảy ra khi `2\sqrt{x}-3=0<=>2\sqrt{x}=3<=>x=9/4`
Vậy `GTNN=0` khi `x=9/4`