D= (5+x)/(√x+3) – (x-5)/(√x-3) : 5-3√x/x-9

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1. Giải thích các bước giải:

   `D=(\frac{5+x}{\sqrt{x}+3}-\frac{x-5}{\sqrt{x}-3}):\frac{5-3\sqrt{x}}{x-9}`

   `={(\sqrt{x}-3)(5+x)-(\sqrt{x}+3)(5-x)}/{(\sqrt{x}+3)(\sqrt{x}+3)}.{(\sqrt{x}-3)(\sqrt{x}-3)}/{5-3\sqrt{x}`

   `={5\sqrt{x}+x\sqrt{x}-15-3x-(x\sqrt{x}-5\sqrt{x}+3x-15)}/{(\sqrt{x}+3)(\sqrt{x}-3)}.(\sqrt{x}+3(\sqrt{x}-3)}/{5-3\sqrt{x}}`

   `=(5\sqrt{x}+x\sqrt{x}-15-3x-x\sqrt{x}+5\sqrt{x}-3x+15).1/{5-3\sqrt{x}}`

   `=(10\sqrt{x}-6x).{1}/{5-3\sqrt{x}}`

   `={10\sqrt{x}-6x}/{5-3\sqrt{x}}`

   `=2\sqrt{x}`

   Học tốt!!!

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