Đáp án+Giải thích các bước giải:
`A=x-2\sqrt{x-1}`
`a)ĐK:x-1>=0`
`<=>x>=1`
`b)x=17`
`=>A=17-2\sqrt{17-1}`
`=>A=17-2.\sqrt{16}`
`=>A=17-2.4`
`=>A=17-8`
`=>A=9`
`c)A=x-2\sqrt{x-1}`
`A=x-1-2\sqrt{x-1}+1`
`A=(\sqrt{x-1}-1)^2>=0AAx>=1`
`A=2`
`<=>(\sqrt{x-1}-1)^2=2`
`<=>|\sqrt{x-1}-1|=\sqrt{2}`
`<=>\sqrt{x-1}-1=\sqrt{2}`
`<=>\sqrt{x-1}=\sqrt2+1`
`<=>x-1=3+2\sqrt2`
`<=>x=4+2\sqrt2(tm)`