Mod tham khảo:
3/ (DKXDx>0:x khác 1)
$\dfrac{(\sqrt{x}-1)(x+\sqrt{x}+1)}{\sqrt{x}(\sqrt{x}-1)}+$ $\dfrac{(\sqrt{x}+1)(x-\sqrt{x}+1)}{\sqrt{x}(\sqrt{x}+1)}$
$=$$\dfrac{x+\sqrt{x}+1-x+\sqrt{x}-1}{\sqrt{x}}=$ $\dfrac{2\sqrt{x}}{\sqrt{x}}=2$
4/
$\dfrac{(1+\sqrt{x})^2-4\sqrt{x}}{1-\sqrt{x}}=$ $\dfrac{1+2\sqrt{x}+x-4\sqrt{x}}{1-\sqrt{x}}=$ $\dfrac{(1-\sqrt{x})^2}{1-\sqrt{x}}=1-\sqrt{x}$
5/$x;y>0$
$\dfrac{(\sqrt{x}+\sqrt{y})(x+y-\sqrt{x}\sqrt{y})}{x-\sqrt{xy}+y}.(\sqrt{x}-\sqrt{y})=x-y$
6/ĐKXĐ:$x≥0$
$\dfrac{\sqrt{x^3}-\sqrt{x}+2x-2}{\sqrt{x}+2}=$ $\dfrac{(\sqrt{x}+2)(x-1)}{\sqrt{x}+2}=x-1$
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