Đáp án `+` Giải thích các bước giải:

`A = ((3\sqrt{x})/(\sqrt{x}-1) - 1/(\sqrt{x} + 1) - 3). (\sqrt{x} + 1)/(\sqrt{x} +2)`

`= [[3\sqrt{x} . (\sqrt{x}+1)]/[(\sqrt{x}-1).(\sqrt{x}+1)] - [1.(\sqrt{x}-1)]/[(\sqrt{x}-1).(\sqrt{x}+1)] - [3.(\sqrt{x}-1).(\sqrt{x}+1)]/[(\sqrt{x}-1).(\sqrt{x}+1)]] .(\sqrt{x} + 1)/(\sqrt{x} +2)` 

`= [(3\sqrt{x} . (\sqrt{x}+1) - [1.(\sqrt{x}-1)] - [3.(\sqrt{x}-1).(\sqrt{x}+1)]]/[(\sqrt{x}-1).(\sqrt{x}+1)]] .(\sqrt{x} + 1)/(\sqrt{x} +2)` 

`= (3x + 3\sqrt{x} - \sqrt{x} + 1 -3x + 3)/[(\sqrt{x}-1).(\sqrt{x}+1)].(\sqrt{x} + 1)/(\sqrt{x} +2)`

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

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

`= 2/(\sqrt{x}-1)                (x >= 0)`

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