Giúp mk với nha. Cần gấp. RÚT GỌN

`A=[\sqrt{x+4\sqrt{x-4}}+\sqrt{x-4\sqrt{x-4}}]/[\sqrt{1-8/x +16/[x^2]}]`     `ĐK: x > 4`

`A=[\sqrt{(\sqrt{x-4}+2)^2}+\sqrt{(\sqrt{x-4}-2)^2}]/[\sqrt{(1-4/x)^2}`

`A=[|\sqrt{x-4}+2|+|\sqrt{x-4}-2|]/[|1-4/x|]`

`A=[\sqrt{x-4}+2+|\sqrt{x-4}-2|]/[1-4/x]`

`@TH1: 4 < x < 8`

  `=>A=[\sqrt{x-4}+2+2-\sqrt{x-4}]/[1-4/x]=[4x]/[x-4]`

`@TH2: x >= 8`

  `=>A=[\sqrt{x-4}+2+\sqrt{x-4}-2]/[1-4/x]=[2x]/\sqrt{x-4}`