1 câu trả lời
`#tnvt`
`A=\sqrt{2x^2-4x+5}+2`
`=\sqrt{2x^2-4x+2+3}+2`
`=\sqrt{2(x^2-2x+1)+3}+2`
`=\sqrt{2(x-1)^2+3}+2`
`∀x` ta có: `(x-1)^2>=0`
`=>2(x-1)^2>=0`
`=>2(x-1)^2+3>=3`
`=>\sqrt{2(x-1)^2+3}>=\sqrt{3}`
`=>\sqrt{2(x-1)^2+3}+2>=\sqrt{3}+2`
Dấu `=` xảy ra khi `x-1=0<=>x=1`
Vậy `GTNNNN_A=\sqrt{3}+2` khi `x=1`