Đáp án:
a) ĐK xác định : `x`$\neq$ `9` ; `x`$\geq$`0`
b)`A=``(x-6\sqrt{x}+9)/(\sqrt{x}-3)``+``(x+4\sqrt{x}+4)/(\sqrt{x}+2)`
`=``(\sqrt{x}²-2\sqrt{x}3+9)/(\sqrt{x}-3)``+``(\sqrt{x}²+2\sqrt{x}2+4)/(\sqrt{x}+2)`
`=``((\sqrt{x}-3)²)/(\sqrt{x}-3)``+``((\sqrt{x}+2)²)/(\sqrt{x}+2)`
`=`$\sqrt{x}$`-3+`$\sqrt{x}$`+2`
`=``2`$\sqrt{x}$`-1`
c) `A=``2`$\sqrt{25/16}$`-1`
`=``2.``5/4``-1`
`=``5/2``-1`
`=``3/2`