Đáp án+Giải thích các bước giải:
\(1.\\\dfrac{\sqrt{x}}{\sqrt{x}+5}+\dfrac{2\sqrt{x}}{\sqrt{x}+5}-\dfrac{3x+25}{x-25}\\(x> 5, x\ne 25)\\= \dfrac{\sqrt{x}}{\sqrt{x}-5} +\dfrac{2\sqrt{x}}{\sqrt{x}-5}-\dfrac{3x+25}{(\sqrt{x}-5)(\sqrt{x}+5)}\\= \dfrac{(\sqrt{x}-5)\sqrt{x}+2\sqrt{x}(\sqrt{x}+5)-(3x+25)}{(\sqrt{x}-5)(\sqrt{x}+5)}\\=\dfrac{x-5\sqrt{x}+2x +10\sqrt{x}-3x -25}{(\sqrt{x}-5)(\sqrt{x}+5)}\\= \dfrac{5\sqrt{x}-25}{(\sqrt{x}-5)(\sqrt{x}+5)}\\= \dfrac{5(\sqrt{x}-5)}{(\sqrt{x}-5)(\sqrt{x}+5)}\\= \dfrac{5}{\sqrt{x}+5}\\2.\\P= \dfrac{2}{7}\\\Rightarrow \dfrac{5}{\sqrt{x}+5} = \dfrac{2}{7}\\(x\ge 0)\\\Leftrightarrow 35 =2(\sqrt{x}+5)\\\Leftrightarrow 35 = 2\sqrt{x}+10\\\Leftrightarrow -2\sqrt{x}= -25\\\Leftrightarrow \sqrt{x}=\dfrac{25}{2}\\\Leftrightarrow x= \dfrac{625}{2} \)
