Đáp án: $D=-\dfrac{x-1}{\sqrt{x}}$
Giải thích các bước giải:
Ta có:
$D=\left(\dfrac{\sqrt{x}}{2}-\dfrac{1}{2\sqrt{x}}\right)^2\cdot \left(\dfrac{\sqrt{x}-1}{\sqrt{x}+1}-\dfrac{\sqrt{x}+1}{\sqrt{x}-1}\right)$
$\to D=\left(\dfrac{\sqrt{x}\cdot \sqrt{x}-1}{2\sqrt{x}}\right)^2\cdot \dfrac{\left(\sqrt{x}-1\right)^2-\left(\sqrt{x}+1\right)^2}{\left(\sqrt{x}+1\right)\left(\sqrt{x}-1\right)}$
$\to D=\left(\dfrac{x-1}{2\sqrt{x}}\right)^2\cdot \dfrac{-4\sqrt{x}}{x-1}$
$\to D=\dfrac{\left(x-1\right)^2}{4x}\cdot \dfrac{-4\sqrt{x}}{x-1}$
$\to D=-\dfrac{x-1}{\sqrt{x}}$
